WorldWideScience

Sample records for derived zirconia based

  1. Zirconia based ceramics

    International Nuclear Information System (INIS)

    Bressiani, J.C.; Bressiani, A.H.A.

    1989-05-01

    Within the new generation of ceramic materials, zirconia continues to attract ever increasing attention of scients, technologists and users by virtue of its singular combination of properties and being able to perform thermo-mechanical, electroeletronic, chemico-biological functions. Nevertheless, in order to obtain these properties, a through understanding of the phase transformation mechanisms and microstructural changes is necessary. This paper discusses the main parameters that require control during fabrication of these materials to obtain desired properties for a specific application. (author) [pt

  2. Zirconia based ceramics

    International Nuclear Information System (INIS)

    Bressiani, J.C.; Bressiani, A.H.A.

    1988-01-01

    Within the new generation of ceramic materials, zirconia continues to attract ever increasing attention of scientists, technologists and users by virtue of its singular combination of properties and being able to perform thermo-mechanical, electro-electronic, chemico-biological functions. Nevertheless, in order to obtain these properties, a through understanding of the phase transformation mechanisms and microstructural changes is necessary. This paper discusses the main parameters that require control during fabrication of these materials to obtain desired properties for a specific application. (author) [pt

  3. Zirconia-based colors for ceramic glazes

    International Nuclear Information System (INIS)

    Eppler, R.A.

    1977-01-01

    The history of color development for use in ceramic glazes is outlined. The most significant modern development is based on zirconia and zircon. These materials have gained increasing acceptance in the industry since their introduction in the late 1950's and early 1960's, due to their superior stability during firing of the glaze

  4. Sol-gel derived bioactive coating on zirconia: Effect on flexural strength and cell proliferation.

    Science.gov (United States)

    Shahramian, Khalil; Leminen, Heidi; Meretoja, Ville; Linderbäck, Paula; Kangasniemi, Ilkka; Lassila, Lippo; Abdulmajeed, Aous; Närhi, Timo

    2017-11-01

    The purpose of this study was to evaluate the effect of sol-gel derived bioactive coatings on the biaxial flexural strength and fibroblast proliferation of zirconia, aimed to be used as an implant abutment material. Yttrium stabilized zirconia disc-shaped specimens were cut, ground, sintered, and finally cleansed ultrasonically in each of acetone and ethanol for 5 minutes. Three experimental groups (n = 15) were fabricated, zirconia with sol-gel derived titania (TiO 2 ) coating, zirconia with sol-gel derived zirconia (ZrO 2 ) coating, and non-coated zirconia as a control. The surfaces of the specimens were analyzed through images taken using a scanning electron microscope (SEM), and a non-contact tapping mode atomic force microscope (AFM) was used to record the surface topography and roughness of the coated specimens. Biaxial flexural strength values were determined using the piston-on-three ball technique. Human gingival fibroblast proliferation on the surface of the specimens was evaluated using AlamarBlue assay™. Data were analyzed using a one-way analysis of variance (ANOVA) followed by Tukey's post-hoc test. Additionally, the biaxial flexural strength data was also statistically analyzed with the Weibull distribution. The biaxial flexural strength of zirconia specimens was unaffected (p > 0.05). Weibull modulus of TiO 2 coated and ZrO 2 coated groups (5.7 and 5.4, respectively) were lower than the control (8.0). Specimens coated with ZrO 2 showed significantly lower fibroblast proliferation compared to other groups (p sol-gel derived coatings have no influence on the flexural strength of zirconia. ZrO 2 coated specimens showed significantly lower cell proliferation after 12 days than TiO 2 coated or non-coated control. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2401-2407, 2017. © 2016 Wiley Periodicals, Inc.

  5. Natural radioactivity in zirconia-based dental ceramics

    International Nuclear Information System (INIS)

    Giussani, Augusto; Gerstmann, Udo; La Porta, Caterina; Cantone, Marie C.; Veronese, Ivan

    2008-01-01

    Zirconia-based ceramics are being increasingly used in dental prosthetics in substitution of metal cores, which are known to induce local toxic reactions and delayed allergic responses in the oral tissues. Some concerns have been however raised about the use of zirconia, since it is known that unpurified zirconia materials may contain non negligible levels of natural radionuclides of the U/Th series. Combined measurements of alpha and gamma spectrometry as well as beta dosimetry were conducted on zirconia samples used for dental applications. Samples were available in form of powder and/or solid blocks. The results showed that the beta dose rate in zirconia ceramics was on average only slightly higher than the levels measured in natural teeth, and generally lower than the values measured in feldspatic and glass ceramics. These materials are indeed known to deliver a beta dose significantly higher than that measured from natural teeth, due to the relatively high levels of 40 K (between 2 and 3 kBq·kg -1 ). The content of radionuclides of the U/Th series in the zirconia sample was estimated to be lower than 15 Bq·kg -1 , i.e. doubtlessly below the exclusion level of 1 kBq·kg -1 recommended by IAEA in the Safety Standard Series. Beta dosimetry measurements, however, gave indications of possible inhomogeneous clusters of radioactivity, which might give rise to local doses above the background. (author)

  6. Magnetic resonance imaging in zirconia-based dental implantology.

    Science.gov (United States)

    Duttenhoefer, Fabian; Mertens, Marianne E; Vizkelety, Josef; Gremse, Felix; Stadelmann, Vincent A; Sauerbier, Sebastian

    2015-10-01

    X-ray-based planning and post-implantation assessment of titanium implants is the commonly accepted standard to date. However, new implant materials such as zirconia (ZrO2 ) have become available, and magnetic resonance imaging may be a valuable alternative with these implants. The present in vitro study investigated artifacts produced by titanium and zirconia implants in magnetic resonance imaging (MRI) and assessed the accuracy of pre-implant planning and post-implantation assessment comparing MRI to standard X-ray-based imaging modalities: Orthopantomogram (OPT), cone beam (CBCT), and computed tomography (CT). Twelve porcine mandibles were prepared and scanned (MRI, OPT, CBCT, μCT), and bone height above the nerve canal was measured. Specimens were implanted with either two titanium or zirconia implants and rescanned to investigate the influence of implant materials on post-implantation assessment. MRI and μCT artifacts were quantified with implants embedded in gelatin phantoms and porcine specimens. Compared with CBCT set as standard, μCT, OPT, and MRI showed similar accuracy in pre-op bone height measurements. Post-implantation, while titanium implants induced a strong B0 -field distortion resulting in extensive signal voids, zirconia implants were clearly depictable with only minor distortions. Excellent contrast, limited artifacts, radiation-free and accurate implant assessment may indicate that MRI is a valuable imaging alternative for zirconia-based implant dentistry. © 2014 The Authors. Clinical Oral Implants Research Published by John Wiley & Sons Ltd.

  7. The effective design of zirconia coping on titanium base in dental implant superstructure.

    Science.gov (United States)

    Mieda, Maiko; Atsuta, Ikiru; Matsushita, Yasuyuki; Morita, Takehiro; Ayukawa, Yasunori; Tsukiyama, Yoshihiro; Sawae, Yoshinori; Koyano, Kiyoshi

    2018-03-30

    Zirconia exhibits good tissue compatibility and nontoxicity, making it a widely used esthetic replacement material for implant abutments. To avoid abutment-fracture, the parts composed of zirconia with a bonded metal component connected to the implant can be used. The purpose of this study was to design titanium and zirconia components with high fracture resistance at the zirconia component's edge line. Three edge line designs of the titanium base and zirconia sleeve were made: chamfer, shoulder, and back-taper. To assess the strength of the abutment design, static loads were applied vertically and 30 degrees from the vertical axis. A test of tensile strength was also performed after chewing simulation. Conventional zirconia components mounted on a chamfer-type titanium base showed significantly lower fracture resistance than shoulder and back-taper types. This study suggests that to improve the durability of zirconia abutments with a titanium base, a back-tapered edge design is recommended.

  8. Cellular transcriptional response to zirconia-based implant materials.

    Science.gov (United States)

    Altmann, Brigitte; Rabel, Kerstin; Kohal, Ralf J; Proksch, Susanne; Tomakidi, Pascal; Adolfsson, Erik; Bernsmann, Falk; Palmero, Paola; Fürderer, Tobias; Steinberg, Thorsten

    2017-02-01

    To adequately address clinically important issues such as osseointegration and soft tissue integration, we screened for the direct biological cell response by culturing human osteoblasts and gingival fibroblasts on novel zirconia-based dental implant biomaterials and subjecting them to transcriptional analysis. Biomaterials used for osteoblasts involved micro-roughened surfaces made of a new type of ceria-stabilized zirconia composite with two different topographies, zirconium dioxide, and yttria-stabilized zirconia (control). For fibroblasts smooth ceria- and yttria-stabilized zirconia surface were used. The expression of 90 issue-relevant genes was determined on mRNA transcription level by real-time PCR Array technology after growth periods of 1 and 7 days. Generally, modulation of gene transcription exhibited a dual dependence, first by time and second by the biomaterial, whereas biomaterial-triggered changes were predominantly caused by the biomaterials' chemistry rather than surface topography. Per se, modulated genes assigned to regenerative tissue processes such as fracture healing and wound healing and in detail included colony stimulating factors (CSF2 and CSF3), growth factors, which regulate bone matrix properties (e.g. BMP3 and TGFB1), osteogenic BMPs (BMP2/4/6/7) and transcription factors (RUNX2 and SP7), matrix collagens and osteocalcin, laminins as well as integrin ß1 and MMP-2. With respect to the biomaterials under study, the screening showed that a new zirconia-based composite stabilized with ceria may be promising to provide clinically desired periodontal tissue integration. Moreover, by detecting biomarkers modulated in a time- and/or biomaterial-dependent manner, we identified candidate genes for the targeted analysis of cell-implant bioresponse during biomaterial research and development. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  9. A novel urea biosensor based on zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Sumana, G. [Department of Science and Technology Centre on Biomolecular Electronics, Biomedical Instrumentation Section, Materials Physics and Engineering Division, National Physical Laboratory(Council of Scientific and Industrial Research), Dr.K.S.Krishnan Marg, New Delhi 110012 (India); Das, Maumita [Department of Science and Technology Centre on Biomolecular Electronics, Biomedical Instrumentation Section, Materials Physics and Engineering Division, National Physical Laboratory(Council of Scientific and Industrial Research), Dr.K.S.Krishnan Marg, New Delhi 110012 (India); Department of Chemistry, University of Delhi, Delhi-110007 (India); Srivastava, Saurabh [Department of Science and Technology Centre on Biomolecular Electronics, Biomedical Instrumentation Section, Materials Physics and Engineering Division, National Physical Laboratory(Council of Scientific and Industrial Research), Dr.K.S.Krishnan Marg, New Delhi 110012 (India); Malhotra, B.D., E-mail: bansi.malhotra@gmail.co [Department of Science and Technology Centre on Biomolecular Electronics, Biomedical Instrumentation Section, Materials Physics and Engineering Division, National Physical Laboratory(Council of Scientific and Industrial Research), Dr.K.S.Krishnan Marg, New Delhi 110012 (India)

    2010-11-30

    Electrochemically deposited biocompatible zirconia (ZrO{sub 2}) film on gold coated glass electrodes has been utilized for the fabrication of urea biosensor. The prepared ZrO{sub 2} films and bioelectrodes have been characterized using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and electrochemical techniques, respectively. The urea biosensor, fabricated by immobilizing mixed enzyme [urease (Urs) and glutamate dehydrogenase (GLDH)] on this nanobiomaterial, shows linearity up to 40 mg dL{sup -1} of analyte (urea) and sensitivity of 0.071 {mu}A/(mM cm{sup -2}) with stability up to 4 months when stored at 4 {sup o}C. The low value of Michaelis-Menten constant (K{sub m}) estimated using Hans plot as 0.5 mM indicates enhancement in the affinity and/or activity of enzyme attached to this nanostructured biocompatible matrix.

  10. Effects of aqueous and acid-based coloring liquids on the hardness of zirconia restorations.

    Science.gov (United States)

    Nam, Ji-Young; Park, Mi-Gyoung

    2017-05-01

    The effects of the application of aqueous coloring liquids on the mechanical properties of zirconia have not yet been investigated. The purpose of this in vitro study was to evaluate the effects of 3 different coloring techniques and the number of coloring liquid applications on the hardness of zirconia. Eighty specimens were divided into 8 groups (n=10); nonshaded zirconia, preshaded zirconia, acid-based coloring liquid zirconia, and aqueous coloring liquid zirconia (1, 3, 6). Vickers hardness was measured. Data were analyzed via 1-way and 2-way ANOVAs. Multiple comparisons were performed using a Scheffé test (α=.05). Statistically significant differences in hardness were found between acid-based coloring liquid zirconia and aqueous coloring liquid zirconia (Pzirconia (Pzirconia (P>.05). Within the limitations of this study, the hardness of zirconia was influenced to differing degrees depending on coloring technique. The number of coloring liquid applications affected the hardness of zirconia colored with the acid-based coloring liquid but not the hardness of zirconia colored with the aqueous coloring liquid. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  11. Zirconia-based solid state chemical gas sensors

    CERN Document Server

    Zhuiykov, S

    2000-01-01

    This paper presents an overview of chemical gas sensors, based on solid state technology, that are sensitive to environmental gases, such as O sub 2 , SO sub x , NO sub x , CO sub 2 and hydrocarbons. The paper is focussed on performance of electrochemical gas sensors that are based on zirconia as a solid electrolyte. The paper considers sensor structures and selection of electrode materials. Impact of interfaces on sensor performance is discussed. This paper also provides a brief overview of electrochemical properties of zirconia and their effect on sensor performance. Impact of auxiliary materials on sensors performance characteristics, such as sensitivity, selectivity, response time and recovery time, is also discussed. Dual gas sensors that can be applied for simultaneous monitoring of the concentration of both oxygen and other gas phase components, are briefly considered

  12. Different Strategies to Bond Bis-GMA-based Resin Cement to Zirconia.

    Science.gov (United States)

    Lopes, Guilherme Carpena; Spohr, Ana Maria; De Souza, Grace M

    To evaluate the effect of different bonding strategies on short- and long-term bis-GMA-based resin cement bond strengths to zirconia. One hundred twenty samples of fully-sintered zirconia (Prettau Zirconia) were sandblasted and randomly distributed into 5 groups (n = 24): UA: Scotchbond Universal Adhesive; SZP: Signum Zirconia Bond I + II; ZPP: Z-Prime Plus; EXP: MZ experimental primer; CO: no primer application (control). After performing these surface treatments, translucent tubes (0.8 mm diameter and 1.0 mm height) were placed on the zirconia specimens, and bis-GMA-based cement (Duo-Link) was injected into them and light cured. Specimens were tested for microshear bond strength either 24 h or 6 months (m) after water storage (37°C) and surfaces were characterized by SEM and EDX. Two-way ANOVA and Tukey's post-hoc test (p zirconia surface. In these groups, EDX demonstrated the presence of phosphorus. Group ZPP resulted in a nonhomogeneous layer, exposing the zirconia substrate underneath. EXP application resulted in an undetectable layer. Water storage did not affect resin cement bond strengths to zirconia irrespective of the surface treatment. Bis-GMA-based resin cement bond strengths to zirconia are affected by specific bonding strategies.

  13. Microstructure-electrical properties relation of zirconia based ceramic composites

    International Nuclear Information System (INIS)

    Fonseca, Fabio Coral

    2001-01-01

    The electrical properties of zirconia based ceramic composites were studied by impedance spectroscopy. Three materials were prepared with different relative compositions of the conducting and insulating phases: (ZrO 2 :8 mol% Y 2 ) 3 ) + MgO, (ZrO 2 :8 mol% Y 2 O 3 ) + Y 2 O 3 and ZrO 2 + 8 mol% Y 2 O 3 . All specimens were analyzed by X-ray diffraction and scanning electron microscopy for microstructural characterization and for correlation of microstructural aspects with electrical properties. For (ZrO 2 :8 mol% Y 2 O 3 ) + MgO the main results show that the dependence of the different (microstructural constituents) contributions to the electrical resistivity on the magnesia content follows two stages: one below and another above the solubility limit of magnesia in Yttria-stabilized zirconia. The same dependence is found for the lattice parameter determined by X-ray diffraction measurements. The impedance diagrams of the composites have been resolved allowing the identification of contributions due to the presence of each microstructural constituent in both stages. Magnesia as a second phase is found to inhibit grain growth in Yttria-stabilized zirconia and the solubility limit for magnesia in the zirconia matrix is around 10 mol%. For (ZrO 2 :8 mol% Y 2 O 3 ) + Y 2 O 3 the main results show that: Yttria is present as a second phase for 1350 deg C /0.1 h sintering; the addition of 2 mol% of Yttria does not modify significantly the electrical properties; the solubility limit for Yttria is around 2 mol% according to electrical measurements. Similarly to magnesia, Yttria inhibits grain growth on Yttria-stabilized zirconia. The general effective medium theory was used to analyze the percolation of the insulating phase; the percolation threshold is different if one considers separately the total, bulk and grain boundary contributions to the electrical conductivity: 32.0, 38.5 and 27.8 vol% for total, intra and intergranular contributions, respectively. The increase of

  14. Zirconia based ceramics, some clinical and biological aspects: Review

    Directory of Open Access Journals (Sweden)

    Ossama Saleh Abd El-Ghany

    2016-12-01

    Full Text Available Improved material strength, enhanced esthethic and high biocompatibility give Zirconia ceramic a great possibility to be used for a wide range of promising clinical applications. This review presents the different types of zirconia materials available for dental application, the effect of machining procedures on these materials, the esthetic of zirconia ceramics and bonding of the veneering ceramics in addition to the biologic properties of these new materials.

  15. Hydrothermal synthesis and characterization of zirconia based catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Caillot, T., E-mail: Thierry.caillot@ircelyon.univ-lyon1.fr; Salama, Z.; Chanut, N.; Cadete Santos Aires, F.J.; Bennici, S.; Auroux, A.

    2013-07-15

    In this work, three equimolar mixed oxides ZrO{sub 2}/CeO{sub 2}, ZrO{sub 2}/TiO{sub 2}, ZrO{sub 2}/La{sub 2}O{sub 3} and a reference ZrO{sub 2} have been synthesized by hydrothermal method. The structural and surface properties of these materials have been fully characterized by X-ray diffraction, transmission electron microscopy, surface area measurement, chemical analysis, XPS, infrared spectroscopy after adsorption of pyridine and adsorption microcalorimetry of NH{sub 3} and SO{sub 2} probe molecules. All investigated mixed oxides are amphoteric and possess redox centers on their surface. Moreover, hydrothermal synthesis leads to catalysts with higher surface area and with better acid–base properties than classical coprecipitation method. Both Lewis and Brønsted acid sites are present on the surface of the mixed oxides. Compared to the other samples, the ZrO{sub 2}/TiO{sub 2} material appears to be the best candidate for further application in acid–base catalysis. - Graphical abstract: Mesoporous amorphous phase with a high surface area of titania zirconia mixed oxide obtained by hydrothermal preparation. - Highlights: • Three zirconia based catalysts and a reference were prepared by hydrothermal synthesis. • Mixed oxides present larger surface areas than the reference ZrO{sub 2}. • ZrO{sub 2}/TiO{sub 2} catalyst presents a mesoporous structure with high surface area. • ZrO{sub 2}/TiO{sub 2} catalyst presents simultaneously strong acidic and basic properties.

  16. HOT ELUENT CAPILLARY LIQUID CHROMATOGRAPHY USING ZIRCONIA AND TITANIA BASED STATIONARY PHASES. (R825344)

    Science.gov (United States)

    AbstractHigh speed capillary liquid chromatographic separations using a simple home made system constructed from readily available inexpensive components have been studied. Using thermally stable zirconia and titania based packing, the separation of eight alkylbenzene...

  17. Evaluation of zirconia-based posterior single crowns supported by zirconia implants: preliminary results of a prospective multicenter study.

    Science.gov (United States)

    Spies, Benedikt Christopher; Kohal, Ralf-Joachim; Balmer, Marc; Vach, Kirstin; Jung, Ronald E

    2017-05-01

    sensitivity when providing zirconia implants with veneered zirconia-based crowns questioning its suitability for this indication. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  18. Fractographic features of glass-ceramic and zirconia-based dental restorations fractured during clinical function

    OpenAIRE

    Øilo, Marit; Hardang, Anne Dybdahl; Ulsund, Amanda Hembre; Gjerdet, Nils Roar

    2014-01-01

    Fractures during clinical function have been reported as the major concern associated with all-ceramic dental restorations. The aim of this study was to analyze the fracture features of glass-ceramic and zirconia-based restorations fractured during clinical use. Twenty-seven crowns and onlays were supplied by dentists and dental technicians with information about type of cement and time in function, if available. Fourteen lithium disilicate glass-ceramic restorations and 13 zirconia-based res...

  19. Shear Bond Strength of Porcelain to a Base-Metal Compared to Zirconia Core

    Directory of Open Access Journals (Sweden)

    Abrisham SM

    2017-03-01

    Full Text Available Statement of Problem: Recent clinical results for Zirconia all-ceramic restorations have revealed that the fracture rate 6-15% of the Zirconia framework is so low and the core of Zirconia has high stability. However, chipping-off fractures of porcelain are the most common reason for failures of Zirconia in the fixed partial dentures. Objectives: The purpose of this study was to compare the shear bond strength (SBS of porcelain in the porcelain fused to metal and all-ceramic crowns with Zirconia core. Materials and Methods: Two groups were selected: porcelain fused to metal (PFM and porcelain fused to Zirconia (PFZ (n = 30.In the PFM group, a wax model (10 × 10 × 10mmwas used to cast metal base (Ni_Cr alloy. In the PFZ group, an acrylic cubic model (10 × 10 × 10mm was made as Zirconia model for scanning.15 cubic Zirconia samples were milled by CAD-CAM. The procedure of porcelain veneering was conducted by the conventional layering technique up to 2 mm thickness (2.5 × 2.5 × 2 mm. All specimens were stored in water for 48 hrs. Thermal cycling was conducted for 20000 cycles between 55°C and 5ºC alternatively for 30s.All samples were mounted in acrylic resin and the SBS test was performed, using a universal testing machine. The analysis of data was performed at a significance level of 0.05 using Kolmogorov-Smirnov and Mann-Whitney U-test. Results: Mean of SBS in PFM and PFZ was 24.57 and 20.88, respectively. The results of Mann-Whitney test showed that there was no statistically significant difference between the two groups of porcelain fused to metal and Zirconia in item shear bond strength (p = 0.455. Conclusions: There was no significant difference between the two groups of PFM and PFZ in the item SBS.

  20. Shear Bond Strength of Porcelain to a Base-Metal Compared to Zirconia Core.

    Science.gov (United States)

    Abrisham, S M; Fallah Tafti, A; Kheirkhah, S; Tavakkoli, M A

    2017-03-01

    Recent clinical results for Zirconia all-ceramic restorations have revealed that the fracture rate 6-15% of the Zirconia framework is so low and the core of Zirconia has high stability. However, chipping-off fractures of porcelain are the most common reason for failures of Zirconia in the fixed partial dentures. The purpose of this study was to compare the shear bond strength (SBS) of porcelain in the porcelain fused to metal and all-ceramic crowns with Zirconia core. Two groups were selected: porcelain fused to metal (PFM) and porcelain fused to Zirconia (PFZ) (n = 30).In the PFM group, a wax model (10 × 10 × 10mm)was used to cast metal base (Ni_Cr alloy). In the PFZ group, an acrylic cubic model (10 × 10 × 10mm) was made as Zirconia model for scanning.15 cubic Zirconia samples were milled by CAD-CAM. The procedure of porcelain veneering was conducted by the conventional layering technique up to 2 mm thickness (2.5 × 2.5 × 2 mm). All specimens were stored in water for 48 hrs. Thermal cycling was conducted for 20000 cycles between 55°C and 5ºC alternatively for 30s.All samples were mounted in acrylic resin and the SBS test was performed, using a universal testing machine. The analysis of data was performed at a significance level of 0.05 using Kolmogorov-Smirnov and Mann-Whitney U-test. Mean of SBS in PFM and PFZ was 24.57 and 20.88, respectively. The results of Mann-Whitney test showed that there was no statistically significant difference between the two groups of porcelain fused to metal and Zirconia in item shear bond strength ( p = 0.455). There was no significant difference between the two groups of PFM and PFZ in the item SBS.

  1. Fracture resistance of implant-supported screw-retained zirconia-based molar restorations.

    Science.gov (United States)

    Honda, Junichi; Komine, Futoshi; Kamio, Shingo; Taguchi, Kohei; Blatz, Markus B; Matsumura, Hideo

    2017-09-01

    The objective of this in vitro study was to investigate fracture loads of screw-retained zirconia-based molar restorations (hybrid abutment crown) fabricated with different restorative materials and designs. Forty-four screw-retained zirconia-based molar restorations were fabricated on dental implants and divided into four groups (n = 11): porcelain-layered zirconia-based restorations (PLZ), indirect composite-layered zirconia-based restorations (ILZ), metal-ceramic restorations (MC), and monolithic zirconia restorations (MONO). The zirconia-based restorations in the PLZ, ILZ, and MONO groups were adhesively bonded on implant abutments with a dual-polymerized resin material. All restorations were tightened on implant bodies with titanium screws and were tested for fracture resistance. The Kruskal-Wallis test and Steel-Dwass test were used to evaluate differences in fracture loads (α = 0.05). As compared with the other groups, the MONO specimens had a significantly higher mean fracture resistance (7.54 kN); no significant differences were found among the PLZ (1.96 kN), ILZ (1.80 kN), and MC (1.45 kN) groups (P > 0.05). For the PLZ, ILZ, and MC groups, all specimens fractured within the layering materials. In contrast, the fracture mode for the MONO group was complete fracture of the restorations. All restorations withstood the masticatory forces. Fracture loads were significantly higher for screw-retained implant-supported monolithic zirconia restorations than for screw-retained bilayered restorations. For the screw-retained bilayered zirconia-based restorations, the fracture resistance of ILZ restorations was comparable to that of PLZ restorations and MC restorations. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  2. Low Energy Surface Activation of Zirconia Based Restorations.

    Science.gov (United States)

    Aboushelib, Moustafa N

    2016-03-01

    To evaluate the influence of low energy surface activation technique on the biaxial flexure strength of zirconia frameworks. Zirconia discs were prepared by cutting CAD/CAM zirconia blocks. Sintered discs were airborne particle abraded using one of the following particles: 30 μm alumina particles, 50 μm alumina particles, or modified round edges 30 μm alumina particles at low pressure. Scanning electron microscopy, x-ray diffraction analysis, surface roughness, and biaxial flexure strength tests were performed (n = 20). Fractured specimens were fractographically analyzed (α = 0.05). Low energy surface activation resulted in 7% monoclinic crystallographic transformation, increasing surface roughness from 0.05 to 0.3 μm and in significant increase in biaxial flexure strength (1718 MPa) compared 30 μm (1064 MPa), 50 μm (1210 MPa), and as-sintered specimens (1150 MPa). Low energy surface activation of zirconia specimens improved the biaxial flexure strength of zirconia frameworks without creation of surface damage. Clinical implications: by controlling particle size and shape of alumina, the flexure strength of zirconia restorations could be increased usinglow pressure particle abrasion.

  3. Tribological properties of toughened zirconia-based ceramics

    International Nuclear Information System (INIS)

    Stachowiak, G.W.; Stachowiak, G.B.

    1991-01-01

    The physical and mechanical properties of toughened zirconia ceramics are briefly characterized and described with a special emphasis on their tribological behaviour. The wear and friction properties of PSZ and TZP ceramics at room and elevated temperatures are described. The influence of the environment on the tribological characteristics of zirconia ceramics is discussed. Both lubricated and unlubricated conditions for ceramic/ceramic and metal/ceramic sliding contacts are analysed. One of the main, and as yet unresolved problems, lubrication of ceramic at elevated temperatures and/or space environment, is addressed and the possible solutions to the problem are suggested. The critical needs in the research and development area of improving the tribological properties of zirconia ceramics are defined and its future market potentials stated. 30 refs., 2 tabs., 4 figs

  4. Optimization of compressive strength of zirconia based dental ...

    Indian Academy of Sciences (India)

    Administrator

    1316. Table 2. Taguchi L9 orthogonal array for compressive strength. Filler volume levels. Experimental. Compressive. Signal-to-noise ratio composites. Glass. Zirconia. Silica .... compression tool, taking care to align the centre line of its long axis with the ... pendent variable, the more it has influence on the per- formance ...

  5. Alumina and Zirconia Based Layered Composites:Part 1 Preparation

    Czech Academy of Sciences Publication Activity Database

    Hadraba, Hynek; Maca, K.; Chlup, Zdeněk

    2009-01-01

    Roč. 412, - (2009), s. 221-226 ISSN 1013-9826 R&D Projects: GA ČR(CZ) GA106/06/0724 Institutional research plan: CEZ:AV0Z20410507 Keywords : electrophoretic deposition * alumina * zirconia Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  6. Restoring Congenitally Missing Maxillary Lateral Incisors Using Zirconia-Based Resin Bonded Prostheses.

    Science.gov (United States)

    Stylianou, Antigoni; Liu, Perng-Ru; O'Neal, Sandra J; Essig, Milton E

    2016-01-01

    This clinical report describes an alternative treatment modality for the replacement of congenitally missing maxillary lateral incisors in a 17-year-old patient. Zirconia-based resin-bonded fixed partial dentures (RBFPDs) were selected as a viable and conservative treatment option in a young individual with highly aesthetic expectations. Fabrication of all-ceramic RBFPDs followed specific preparation design and features to accommodate two retainers. The zirconia frameworks with bilateral wings were digitally designed and then milled by a computer-aided design and computer-aided manufacturing (CAD/CAM)-controlled milling machine. Zirconia surface was treated with a two-step chairside tribochemical silica-coating/silane coupling surface treatment protocol, and adhesive resin luting cement was used to achieve micromechanical and chemical bonding. Completion of the treatment resulted in a functional and aesthetic successful outcome and a 17-month follow-up presented uneventful. Contemporary adhesive techniques involving resin-bonded zirconia-based prostheses can be utilized successfully and predictably in young patients with single missing teeth when implant therapy is currently not a treatment of choice and a less invasive approach is desired. The zirconia-based resin-bonded prosthesis constitutes a viable and conservative treatment modality for the replacement of missing teeth either congenitally or from another etiology in young patients in which implant therapy and a fixed partial denture are currently contraindicated. © 2015 Wiley Periodicals, Inc.

  7. Pure titanium casting into zirconia-modified magnesia-based investment molds.

    Science.gov (United States)

    Hung, Chun-Cheng; Hou, Guey-Lin; Tsai, Chi-Cheng; Huang, Cheng-Ching

    2004-11-01

    Molten titanium is highly reactive with common mold materials at elevated temperatures. The aim of this investigation was to improve the accuracy of pure titanium casting by adding unreactive zirconia into magnesia-based investment material. An automatic thermal expansion laser-recording machine (TEM-1000/Pantos, Nippon Co.) was used to measure thermal expansion of investment materials. An automatic argon-casting machine (Castmatic-S, Iwatani Co.) was used to cast pure titanium samples. A stereomicroscope was used (Nikon SM-2T, Japan) to measure marginal discrepancy on a metal die. A Vickers microhardness indenter (MXT-50, Matsuzawa Seiki Co.) determined the Vickers hardness (VH) of the titanium samples. Interfacial reactivity of the titanium was evaluated with an X-ray diffractometer (Rigaku D/max VIII, Tokyo, Japan). A dental X-ray machine was used to examine internal porosity of the castings. Data was analysed with paired t-test (p zirconia to a magnesia-based investment material significantly increased its thermal expansion value (p zirconia-added group (p zirconia decreased interfacial reactivity and the VH of titanium. Under appropriately adjusted conditions, the addition of zirconia to magnesia-based mold materials may be used to produce high quality pure titanium castings.

  8. Practice-based clinical evaluation of metal-ceramic and zirconia molar crowns: 3-year results.

    Science.gov (United States)

    Rinke, S; Schäfer, S; Lange, K; Gersdorff, N; Roediger, M

    2013-03-01

    This practice-based study evaluates the clinical performance of conventionally luted metal-ceramic and zirconia molar crowns fabricated with pronounced anatomical core design and a prolonged cooling period of the veneering porcelain. Fifty-three patients were treated from 07/2008 until 07/2009 with either metal-ceramic crowns (MCC) (high-noble alloy + low-fusing porcelain) or zirconia crowns (Cercon System, DeguDent, Germany). Forty-nine patients (30 women/19 men) with 100 restorations (metal-ceramic: 48/zirconia: 52, mean observational period: 36·5 ± 6 months) participated in a clinical follow-up examination and were included in the study. Time-dependent survival (in situ criteria), success (event-free restorations) and chipping rates (defects of the veneering ceramics) were calculated according to the Kaplan-Meier method and analysed in relation to the crown fabrication technique, using a Cox regression model (P zirconia: 2) were recorded (survival rate after 3 years: metal-ceramic: 97·6%, zirconia: 95·2%). Of the metal-ceramic restorations, 90·9% remained event-free (two ceramic fractures, one endodontic treatment), whereas the success rate for the zirconia was 86·8% (two ceramic fractures, one endodontic treatment, one secondary caries). No significant differences in survival (P = 0·53), success (P = 0·49) and ceramic fracture rates (P = 0·57) were detected. The combination of a pronounced anatomical core design and a modified firing of the veneering porcelain for the fabrication of zirconia molar crowns resulted in a 3-year survival, success and chipping rate comparable to MCC. © 2012 Blackwell Publishing Ltd.

  9. Fracture resistance of single-tooth implant-supported zirconia-based indirect composite-layered molar restorations.

    Science.gov (United States)

    Taguchi, Kohei; Komine, Futoshi; Fushiki, Ryosuke; Blatz, Markus B; Kamio, Shingo; Matsumura, Hideo

    2014-08-01

    This study evaluated the fracture resistance of single-tooth implant-supported zirconia-based indirect composite-layered molar restorations. Forty-four titanium abutments (GingiHue Post) were placed on dental implants (Osseotite Implant). Standardized single-tooth cement-retained implant-supported mandibular molar restorations were fabricated for each of four test groups (n = 11) as follows: porcelain-fused-to-metal crowns (PFM), zirconia-based all-ceramic crowns (ZAC), zirconia-based indirect composite-layered crowns primed with Estenia Opaque Primer for zirconia frameworks (ZIC-E), and zirconia-based indirect composite-layered crowns (ZIC). The crowns were luted with a glass-ionomer cement (Ketac Cem Easymix). Fracture resistance (N) was determined by force application of a perpendicular load to the crowns with a universal testing machine. One-way analysis of variance (ANOVA) and the Tukey's HSD test were used to assess differences in fracture resistance values (α = 0.05). Mean fracture resistances (SD) were 3.09 (0.22) kN, 3.11 (0.34) kN, 2.84 (0.21) kN, and 2.50 (0.36) kN for the PFM, ZAC, ZIC-E, and ZIC groups, respectively. Fracture resistance in the ZIC specimens was significantly lower (P zirconia-based indirect composite-layered molar crowns primed with Estenia Opaque Primer for zirconia frameworks (ZIC-E) is comparable to that of porcelain-fused-to-metal (PFM) and zirconia-based all-ceramic (ZAC) restorations. Application of Estenia Opaque Primer to zirconia ceramic framework provides superior fracture resistance in implant-supported zirconia-based indirect composite-layered molar crowns. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  10. Fracture resistance of zirconia-based implant abutments after artificial long-term aging.

    Science.gov (United States)

    Alsahhaf, Abdulaziz; Spies, Benedikt Christopher; Vach, Kirstin; Kohal, Ralf-Joachim

    2017-02-01

    To investigate the survival rate, fracture strength, bending moments, loading to fracture and fracture modes of different designs of zirconia abutments after dynamic loading with thermocycling, and compare these values to titanium abutments. A total of 80 abutment samples were divided into 5 test groups of 16 samples in each group. The study included the following groups, "Group 1" CAD/CAM produced all-zirconia abutments, "Group 2" titanium abutments, "Group 3" zirconia-abutments adhesively luted to a titanium base, "Group 4" prefabricated all-zirconia abutments and "Group 5" zirconia-abutments glass soldered to a titanium base. Half the number of samples in each group was exposed to 1.2 million loading cycles (5-years simulation) in the chewing simulator. The samples that survived the artificial aging were later tested for fracture strength in a universal testing machine. The remaining 8 samples of the group were directly tested for fracture strength. All samples exposed to the 5-years artificial aging survived except of six samples in one group (Group 1). The surviving samples were later fracture tested in the universal testing machine. The bending moments (Ncm) values were as follow: Exposed groups: "Group 1" 94.5Ncm; "Group 2" 599.2Ncm; "Group 3" 477.5Ncm; "Group 4" 314.4Ncm; "Group 5" 509.4Ncm. Non-exposed groups: "Group 1" 269.3Ncm; "Group 2" 474.2Ncm; "Group 3" 377.6Ncm; "Group 4" 265.4Ncm; "Group 5" 372.4Ncm. Except in Group 1, the values were higher in the exposed groups, although, statistically there was no difference (p>0.05). The one-piece ZrO2-abutment group (Group 1 and Group 4) exhibited lower values, while the two-piece ZrO2-abutment groups (Group 3 and Group 5) showed similar values and fracture modes like the titanium abutment group. The titanium abutment group showed the highest values of bending moments among all groups. The implant-abutment connection area appeared to influence the bending moment value and the fracture mode of the tested

  11. Evaluation of Zirconia-Based All-Ceramic Single Crowns and Fixed Dental Prosthesis on Zirconia Implants: 5-Year Results of a Prospective Cohort Study.

    Science.gov (United States)

    Spies, Benedikt Christopher; Stampf, Susanne; Kohal, Ralf-Joachim

    2015-10-01

    The objective of this 5-year cohort investigation was to determine the survival and success rate of all-ceramic reconstructions on zirconia oral implants. Ninety-three patients received 122 one-piece zirconia implants. One hundred seventeen implants were restored with 63 single crowns (SCs) and 27 three-unit bridges (fixed dental prostheses, FDPs) fabricated using zirconia frameworks (Procera(®) Zirconia, Nobel Biocare(®), Göteborg, Sweden) hand-layered with a silicate ceramic (NobelRondo(™) Zirconia, Nobel Biocare(®)). With any occurrence of chipping regarded as an event, Kaplan-Meier success curves were plotted. Covariates (gender, location, manufacturing date) were estimated by the use of log-rank tests. Eighty-nine patients received prosthetic reconstructions. Sixty-three of them were seen at the 5-year follow-up, with a mean observation time of 58.2 months (47 patients with SCs, 16 patients with FDPs). Reasons for the decreasing number of patients at the follow-up sessions included dropouts due to implant loss (n = 21), moving (n = 3), missed appointments (n = 1), and severe illness (n = 1). Over half of the SCs (57.2%) and 38% of the FDPs were successful after an observation time of 5 years (overall success rate of 51.7%). The performed log-rank tests revealed no statistically significant differences for the success curves regarding the above-mentioned covariates. Among the 63 restorations that completed the study, 11 of 47 SCs and one of 16 FDPs had to be replaced due to the severity of the observed chipping. This results in survival rates of 76.6% for the SCs and 93.8% for the FDPs. No framework fractures or decementations were observed in any group. Hand-layering of zirconia-based SCs and FDPs with NobelRondo(™) Zirconia restoring one-piece zirconia implants did not show acceptable survival and success rates. Meanwhile, the material has been recalled from the market. It is advised that new materials should undergo adequate preclinical evaluation

  12. Superplasticity and joining of zirconia-based ceramics

    International Nuclear Information System (INIS)

    Dominguez-Rodriguez, A.; Gutierrez-Mora, F.; Jimenez-Melendo, M.; Chaim, R.; Routbort, J. L.

    1999-01-01

    Steady-state creep and joining of alumina/zirconia composites containing alumina volume fractions of 20, 60, and 85% have been investigated between 1,250 and 1,350 C. Superplasticity of these compounds is controlled by grain-boundary sliding and the creep rate is a function of alumina volume fraction, not grain size. Using the principles of superplasticity, pieces of the composite have been joined by applying the stress required to achieve 5 to 10% strain to form a strong interface at temperatures as low as 1,200 C

  13. Superplasticity and joining of zirconia-based ceramics

    International Nuclear Information System (INIS)

    Gutierrez-Mora, F.; Dominguez-Rodriguez, A.; Jimenez-Melendo, M.; Chaim, R.; Ravi, G.B.; Routbort, J.L.

    2000-01-01

    Steady-state creep and joining of alumina/zirconia composites containing alumina volume fractions of 20, 60 and 85% have been investigated between 1,250 and 1,350 C. Superplasticity of these compounds is controlled by grain-boundary sliding and the creep rate is a function of alumina volume fraction, not grain size. Using the principles of superplasticity, pieces of the composite have been joined by applying the stress required to achieve 5 to 10% strain to form a strong interface at temperatures as low as 1,200 C

  14. Superplasticity and joining of zirconia-based ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Dominguez-Rodriguez, A.; Gutierrez-Mora, F.; Jimenez-Melendo, M.; Chaim, R.; Routbort, J. L.

    1999-12-10

    Steady-state creep and joining of alumina/zirconia composites containing alumina volume fractions of 20, 60, and 85% have been investigated between 1,250 and 1,350 C. Superplasticity of these compounds is controlled by grain-boundary sliding and the creep rate is a function of alumina volume fraction, not grain size. Using the principles of superplasticity, pieces of the composite have been joined by applying the stress required to achieve 5 to 10% strain to form a strong interface at temperatures as low as 1,200 C.

  15. Chemically Derived Dense Alumina-Zirconia Composites for Improved Mechanical and Wear Erosion Properties

    Science.gov (United States)

    1998-01-01

    As a result of this funded project high purity Zirconia-Toughened Alumina (ZTA) ceramic powders with and without yttria were produced using metal alkoxide precursors. ZTA ceramic powders with varying volume percents of zirconia were prepared (7, 15, and 22%). Aluminum tri-sec butoxide, zirconium propoxide, and yttrium isopropoxide were the reagents used. Synthesis conditions were varied to control the hydrolysis and the aging conditions for the sol to gel transition. FTIR analysis and rheological characterization were used to follow the structural evolution during the sol to gel transition. The greater extent of hydrolysis and the build-up of structure measured from viscoelastic properties were consistent. Heat treatment was conducted to produce submicron grain fully crystalline ZTA ceramic powders. This improved materials should have enhanced properties such strength, toughness, and wear resistance for advanced structural applications, for example engine components in high technology aerospace applications.

  16. Current status of zirconia restoration.

    Science.gov (United States)

    Miyazaki, Takashi; Nakamura, Takashi; Matsumura, Hideo; Ban, Seiji; Kobayashi, Taira

    2013-10-01

    During the past decade, zirconia-based ceramics have been successfully introduced into the clinic to fabricate fixed dental prostheses (FDPs), along with a dental computer-aided/computer-aided manufacturing (CAD/CAM) system. In this article (1) development of dental ceramics, (2) the current status of dental CAD/CAM systems, (3) CAD/CAM and zirconia restoration, (4) bond between zirconia and veneering ceramics, (5) bond of zirconia with resin-based luting agents, (6) surface finish of zirconia restoration and antagonist enamel wear, and (7) clinical evaluation of zirconia restoration are reviewed. Yttria partially stabilized tetragonal zirconia polycrystalline (Y-TZP) showed better mechanical properties and superior resistance to fracture than other conventional dental ceramics. Furthermore, ceria-stabilized tetragonal zirconia polycrystalline and alumina nanocomposites (Ce-TZP/A) had the highest fracture toughness and had resistance to low-temperature aging degradation. Both zirconia-based ceramics have been clinically available as an alternative to the metal framework for fixed dental prostheses (FDPs). Marginal adaptation of zirconia-based FDPs is acceptable for clinical application. The most frequent clinical complication with zirconia-based FDPs was chipping of the veneering porcelain that was affected by many factors. The mechanism for the bonding between zirconia and veneering ceramics remains unknown. There was no clear evidence of chemical bonding and the bond strength between zirconia and porcelain was lower than that between metal and porcelain. There were two alternatives proposed that might avoid chipping of veneering porcelains. One was hybrid-structured FDPs comprising CAD/CAM-fabricated porcelain parts adhering to a CAD/CAM fabricated zirconia framework. Another option was full-contour zirconia FDPs using high translucent zirconia. Combined application of silica coating and/or silane coupler, and 10-methacryloyloxydecyl dihydrogen phosphate is

  17. Cellular viability and genetic expression of human gingival fibroblasts to zirconia with enamel matrix derivative (Emdogain®).

    Science.gov (United States)

    Kwon, Yong-Dae; Choi, Hyun-Jung; Lee, Heesu; Lee, Jung-Woo; Weber, Hans-Peter; Pae, Ahran

    2014-10-01

    The objective of this study was to investigate the biologic effects of enamel matrix derivative (EMD) with different concentrations on cell viability and the genetic expression of human gingival fibroblasts (HGF) to zirconia surfaces. Immortalized human gingival fibroblasts (HGF) were cultured (1) without EMD, (2) with EMD 25 µg/mL, and (3) with EMD 100 µg/mL on zirconia discs. MTT assay was performed to evaluate the cell proliferation activity and SEM was carried out to examine the cellular morphology and attachment. The mRNA expression of collagen type I, osteopontin, fibronectin, and TGF-β1 was evaluated with the real-time polymerase chain reaction (RT-PCR). From MTT assay, HGF showed more proliferation in EMD 25 µg/mL group than control and EMD 100 µg/mL group (P<.05). HGFs showed more flattened cellular morphology on the experimental groups than on the control group after 4h culture and more cellular attachments were observed on EMD 25 µg/mL group and EMD 100 µg/mL group after 24h culture. After 48h of culture, cellular attachment was similar in all groups. The mRNA expression of type I collagen increased in a concentration dependent manner. The genetic expression of osteopontin, fibronectin, and TGF-β1 was increased at EMD 100 µg/mL. However, the mRNA expression of proteins associated with cellular attachment was decreased at EMD 25 µg/mL. Through this short term culture of HGF on zirconium discs, we conclude that EMD affects the proliferation, attachment, and cell morphology of HGF cells. Also, EMD stimulates production of extracellular matrix collagen, osteopontin, and TGF-β1 in high concentration levels. With the use of EMD, protective barrier between attached gingiva and transmucosal zirconia abutment may be enhanced leading to final esthetic results with implants.

  18. Regenerable Subnanometer Pd Clusters on Zirconia for Highly Selective Hydrogenation of Biomass-Derived Succinic Acid in Water

    Directory of Open Access Journals (Sweden)

    Chi Zhang

    2016-07-01

    Full Text Available The size of metal particles is an important factor to determine the performance of the supported metal catalysts. In this work, we report subnanometer Pd clusters supported on zirconia by the microwave-assisted hydrothermal method. The presence of subnanometer Pd clusters on the zirconia surface was confirmed by two-dimensional Gaussian-function fits of the aberration-corrected high-angle annual dark-field images. These subnanometer Pd catalysts exhibit high catalytic performance for the hydrogenation of biomass-derived succinic acid to γ-butyrolactone in water and avoid the formation of overhydrogenated products, such as 1,4-butanediol and tetrahydrofuran. The catalyst with an ultra-low Pd loading of 0.2 wt. % demonstrated high selectivity (95% for γ-butyrolactone using water as a solvent at 473 K and 10 MPa. Moreover, it can be reused at least six times without the loss of catalytic activity, illustrating high performance of the small Pd clusters.

  19. Effects of framework design and layering material on fracture strength of implant-supported zirconia-based molar crowns.

    Science.gov (United States)

    Kamio, Shingo; Komine, Futoshi; Taguchi, Kohei; Iwasaki, Taro; Blatz, Markus B; Matsumura, Hideo

    2015-12-01

    To evaluate the effects of framework design and layering material on the fracture strength of implant-supported zirconia-based molar crowns. Sixty-six titanium abutments (GingiHue Post) were tightened onto dental implants (Implant Lab Analog). These abutment-implant complexes were randomly divided into three groups (n = 22) according to the design of the zirconia framework (Katana), namely, uniform-thickness (UNI), anatomic (ANA), and supported anatomic (SUP) designs. The specimens in each design group were further divided into two subgroups (n = 11): zirconia-based all-ceramic restorations (ZAC group) and zirconia-based restorations with an indirect composite material (Estenia C&B) layered onto the zirconia framework (ZIC group). All crowns were cemented on implant abutments, after which the specimens were tested for fracture resistance. The data were analyzed with the Kruskal-Wallis test and the Mann-Whitney U-test with the Bonferroni correction (α = 0.05). The following mean fracture strength values (kN) were obtained in UNI design, ANA design, and SUP design, respectively: Group ZAC, 3.78, 6.01, 6.50 and Group ZIC, 3.15, 5.65, 5.83. In both the ZAC and ZIC groups, fracture strength was significantly lower for the UNI design than the other two framework designs (P = 0.001). Fracture strength did not significantly differ (P > 0.420) between identical framework designs in the ZAC and ZIC groups. A framework design with standardized layer thickness and adequate support of veneer by zirconia frameworks, as in the ANA and SUP designs, increases fracture resistance in implant-supported zirconia-based restorations under conditions of chewing attrition. Indirect composite material and porcelain perform similarly as layering materials on zirconia frameworks. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  20. Clinical outcomes of zirconia-based implant- and tooth-supported single crowns.

    Science.gov (United States)

    Nejatidanesh, Farahnaz; Moradpoor, Hedayat; Savabi, Omid

    2016-01-01

    Zirconia-based restorations have been increasingly used on implant and teeth abutments, but the evidence about clinical outcomes of these restorations is limited. The aim of this study was to assess up to 7-year clinical outcomes of implant- and tooth-supported zirconia-based single crowns. In this retrospective study, 261 patients with 556 single crowns supported by either teeth (324) or implants (232) were examined during 3- to 7-year follow-up (mean observation of 60.70 months for tooth and 59.20 months for implant-supported crowns). California Dental Association (CDA) quality evaluation system was used to evaluate the restorations. Soft tissue status was assessed using plaque and gingival index scores, bleeding on probing, and pocket depth. Patient and professional satisfaction were evaluated by visual analog scale (VAS). The 5-year Kaplan-Meier survival probability was 98.3 and 97.3 for implant- and tooth-supported crowns, respectively. In regard to CDA rating, most of the crowns were ranked as either excellent or acceptable (99.5 %). The recorded failures were replacement of the crown due to porcelain chipping (3), implant failure (1), and teeth extraction (5). Soft tissue parameters were not affected by the restorations compare to control teeth. The VAS was high for both patients and clinicians. Zirconia-based single crowns on both tooth and implant abutments showed promising clinical performance in this up to 7-year follow-up. The zirconia-based single crowns can be used clinically for tooth- and implant-supported restorations.

  1. Fracture Strength of Titanium based Lithium Disilicate and Zirconia Abutment Crowns

    Science.gov (United States)

    2017-06-12

    If yes . give date. D N/A 27. COMMENTS ~ APPROVED 0 DISAPPROVED I RB approved presentation of dental materials research w i th appropriate...The specimens were cemented to a titanium-base implant system, subjected to thermocycling and cyclic loading, and fractured in a material testing...zirconia abutment/lithium-disilicate crown. INTRODUCTION Dental implants and the use of esthetic abutments are widely practiced procedures for dentists

  2. Fabrication of a zirconia MEMS-based microthruster by gel casting on PDMS soft molds

    International Nuclear Information System (INIS)

    Cheah, K H; Khiew, P S; Chin, J K

    2012-01-01

    A zirconia microelectromechanical-system-based microthruster was fabricated through a newly developed fabrication route. Gel casting of homogenously dispersed zirconia suspension on polydimethylsiloxane soft mold was utilized to replicate the geometries of microthruster design onto a ceramic layer of about 1.2 mm thick. Lamination of the patterned ceramic layer to another flat ceramic layer and subsequent sintering produced the microthruster. Characterizations on the fabricated prototype showed good shape retention on the replicated geometries and good quality of lamination. Shrinkage of about 10–15% was noted after sintering. The current fabrication route is particularly promising for the development of high-performance micropropulsion systems which require their structural material to survive in an extreme environment which is corrosive, of high temperature and highly oxidative. (paper)

  3. Fractographic features of glass-ceramic and zirconia-based dental restorations fractured during clinical function.

    Science.gov (United States)

    Oilo, Marit; Hardang, Anne D; Ulsund, Amanda H; Gjerdet, Nils R

    2014-06-01

    Fractures during clinical function have been reported as the major concern associated with all-ceramic dental restorations. The aim of this study was to analyze the fracture features of glass-ceramic and zirconia-based restorations fractured during clinical use. Twenty-seven crowns and onlays were supplied by dentists and dental technicians with information about type of cement and time in function, if available. Fourteen lithium disilicate glass-ceramic restorations and 13 zirconia-based restorations were retrieved and analyzed. Fractographic features were examined using optical microscopy to determine crack initiation and crack propagation of the restorations. The material comprised fractured restorations from one canine, 10 incisors, four premolars, and 11 molars. One crown was not categorized because of difficulty in orientation of the fragments. The results revealed that all core and veneer fractures initiated in the cervical margin and usually from the approximal area close to the most coronally placed curvature of the margin. Three cases of occlusal chipping were found. The margin of dental all-ceramic single-tooth restorations was the area of fracture origin. The fracture features were similar for zirconia, glass-ceramic, and alumina single-tooth restorations. Design features seem to be of great importance for fracture initiation. © 2014 Eur J Oral Sci.

  4. Fractographic features of glass-ceramic and zirconia-based dental restorations fractured during clinical function

    Science.gov (United States)

    Øilo, Marit; Hardang, Anne D; Ulsund, Amanda H; Gjerdet, Nils R

    2014-01-01

    Fractures during clinical function have been reported as the major concern associated with all-ceramic dental restorations. The aim of this study was to analyze the fracture features of glass-ceramic and zirconia-based restorations fractured during clinical use. Twenty-seven crowns and onlays were supplied by dentists and dental technicians with information about type of cement and time in function, if available. Fourteen lithium disilicate glass-ceramic restorations and 13 zirconia-based restorations were retrieved and analyzed. Fractographic features were examined using optical microscopy to determine crack initiation and crack propagation of the restorations. The material comprised fractured restorations from one canine, 10 incisors, four premolars, and 11 molars. One crown was not categorized because of difficulty in orientation of the fragments. The results revealed that all core and veneer fractures initiated in the cervical margin and usually from the approximal area close to the most coronally placed curvature of the margin. Three cases of occlusal chipping were found. The margin of dental all-ceramic single-tooth restorations was the area of fracture origin. The fracture features were similar for zirconia, glass-ceramic, and alumina single-tooth restorations. Design features seem to be of great importance for fracture initiation. PMID:24698173

  5. Fracture resistance of implant- supported monolithic crowns cemented to zirconia hybrid-abutments: zirconia-based crowns vs. lithium disilicate crowns.

    Science.gov (United States)

    Elshiyab, Shareen H; Nawafleh, Noor; Öchsner, Andreas; George, Roy

    2018-02-01

    The aim of this in vitro study was to investigate the fracture resistance under chewing simulation of implant-supported posterior restorations (crowns cemented to hybrid-abutments) made of different all-ceramic materials. Monolithic zirconia (MZr) and monolithic lithium disilicate (MLD) crowns for mandibular first molar were fabricated using computer-aided design/computer-aided manufacturing technology and then cemented to zirconia hybrid-abutments (Ti-based). Each group was divided into two subgroups (n=10): (A) control group, crowns were subjected to single load to fracture; (B) test group, crowns underwent chewing simulation using multiple loads for 1.2 million cycles at 1.2 Hz with simultaneous thermocycling between 5℃ and 55℃. Data was statistically analyzed with one-way ANOVA and a Post-Hoc test. All tested crowns survived chewing simulation resulting in 100% survival rate. However, wear facets were observed on all the crowns at the occlusal contact point. Fracture load of monolithic lithium disilicate crowns was statistically significantly lower than that of monolithic zirconia crowns. Also, fracture load was significantly reduced in both of the all-ceramic materials after exposure to chewing simulation and thermocycling. Crowns of all test groups exhibited cohesive fracture within the monolithic crown structure only, and no abutment fractures or screw loosening were observed. When supported by implants, monolithic zirconia restorations cemented to hybrid abutments withstand masticatory forces. Also, fatigue loading accompanied by simultaneous thermocycling significantly reduces the strength of both of the all-ceramic materials. Moreover, further research is needed to define potentials, limits, and long-term serviceability of the materials and hybrid abutments.

  6. Sol-gel derived fluor-hydroxyapatite biocoatings on zirconia substrate.

    Science.gov (United States)

    Kim, Hae-Won; Kong, Young-Min; Bae, Chang-Jun; Noh, Yoon-Jung; Kim, Hyoun-Ee

    2004-07-01

    Fluor-hydroxyapatite (FHA) film was coated on a zirconia (ZrO(2)) substrate by a sol-gel method. An appropriate amount of F ions was incorporated into the hydroxyapatite (HA) during the preparation of the sols. The apatite phase began to crystallize after heat treatment at 400 degrees C, and increased in intensity above 500 degrees C. No decomposition was detected by X-ray diffraction analyses up to 800 degrees C, which illustrates the high thermal stability of the FHA films. The films showed a uniform and dense morphology with a thickness of approximately 1 microm after a precisely controlled heat treatment process. These FHA films adhered firmly to the zirconia substrate, representing notable adhesion strengths of approximately 70 MPa after heat treatment above 500 degrees C. The dissolution rate of the FHA coating layer varied according to the heat treatment temperature, which was closely related to the film crystallinity. The dissolution rate of the FHA film was lower than that of the HA film, suggesting the possibility of a functional gradient coating of HA and FHA. The MG63 cells seeded onto the FHA films proliferated in a similar manner to those seeded onto pure HA ceramic and a plastic control.

  7. Effect of the shades of background substructures on the overall color of zirconia-based all-ceramic crowns.

    Science.gov (United States)

    Suputtamongkol, Kallaya; Tulapornchai, Chantana; Mamani, Jatuphol; Kamchatphai, Wannaporn; Thongpun, Noparat

    2013-08-01

    The objective of this study was to determine the effect of the color of a background substructure on the overall color of a zirconia-based all-ceramic crown. Twenty one posterior zirconia crowns were made for twenty subjects. Seven premolar crowns and six molar crowns were cemented onto abutments with metal post and core in the first and second group. In the third group, eight molar crowns were cemented onto abutments with a prefabricated post and composite core build-up. The color measurements of all-ceramic crowns were made before try-in, before and after cementation. A repeated measure ANOVA was used for a statistical analysis of a color change of all-ceramic crowns at α=.05. Twenty four zirconia specimens, with different core thicknesses (0.4-1 mm) were also prepared to obtain the contrast ratio of zirconia materials after veneering. L(*) , a(*) , and b(*) values of all-ceramic crowns cemented either on a metal cast post and core or on a prefabricated post did not show significant changes (P>.05). However, the slight color changes of zirconia crowns were detected and represented by ΔE(*) ab values, ranging from 1.2 to 3.1. The contrast ratios of zirconia specimens were 0.92-0.95 after veneering. No significant differences were observed between the L(*) , a(*) , and b(*) values of zirconia crowns cemented either on a metal cast post and core or a prefabricated post and composite core. However, the color of a background substructure could affect the overall color of posterior zirconia restorations with clinically recommended core thickness according to ΔE(*) ab values.

  8. Seven-year prospective clinical study on zirconia-based single crowns and fixed dental prostheses.

    Science.gov (United States)

    Tartaglia, Gianluca M; Sidoti, Ernesto; Sforza, Chiarella

    2015-06-01

    Zirconia-based prostheses are used for esthetic crown and fixed restorations, but follow-ups are still limited. The authors evaluated the 7-year clinical results of 303 zirconia core restorations, performed in a general dental private practice. Clinical events (fracture and loss of retention, gingivitis, tenderness, excess cement, and temporary pain) were recorded in 303 zirconia core restorations positioned in 88 patients. Kaplan-Meier survival probability estimates were computed for failures (needed the replacement or removal of the prosthesis) and complications (resolved without replacing the prosthesis). One hundred and fifty single crowns (130 tooth-supported, 20 implant-supported) and 153 multiple units up to 6 elements (49 tooth-supported, 104 implant-supported) were followed-up for 7 years in 88 patients (40 men, 48 women), aged 35-89 years (mean 57). During the follow-up period, there were no complications for 287 (95 %) of the restorations. Sixteen restorations/abutment teeth (5 %) had some complication: extraction of abutment tooth (7, 2 %); caries (2, 1 %), porcelain veneer fracture (3, 1 %), loss of retention (4, 1 %). Nine (3 %) restorations were recorded as failures. The overall 7-year survival probability estimate for failures was 0.966 (95 % confidence limits, 0.932 and 0.983), for complications was 0.976 (95 % confidence limits 0.947 and 0.989), with a cumulative survival rate of 94.7 %. Within the analyzed follow-up, zirconia core restorations appear a good clinical solution, with favorable functional properties. All ceramic restorations can be successfully used for both single-and multiple-unit prostheses, either teeth or implants supported.

  9. Performance of a carbon monoxide sensor based on zirconia-doped ceria

    Directory of Open Access Journals (Sweden)

    Noriya Izu

    2016-06-01

    Full Text Available Resistive-type carbon monoxide sensors were fabricated using zirconia-doped ceria, and their sensing properties were evaluated and compared with equivalent devices based on non-doped ceria. The response of both sensor types was found to increase with decreasing temperature, while the response at 450 °C of a sensor fired at 950 °C was greater than that of a sensor fired at 1100 °C. When fired at 950 °C, however, the response at 450 °C of a sensor created using zirconia-doped ceria was slightly less than that of a sensor constructed from non-doped ceria. Multivariate analysis confirmed that the response of both sensor types is proportional to the resistance raised to the power of about 0.5, and inversely proportional to the particle size raised to a power of about 0.8. The sensor response time can be considered almost the same regardless of whether zirconia doping is used or not.

  10. Prospective cohort clinical study assessing the 5-year survival and success of anterior maxillary zirconia-based crowns with customized zirconia copings.

    Science.gov (United States)

    Dogan, Sami; Raigrodski, Ariel J; Zhang, Hai; Mancl, Lloyd A

    2017-02-01

    Studies evaluating anterior zirconia-based crowns are limited. The purpose of this prospective cohort clinical study was to assess the efficacy of zirconia-based anterior maxillary crowns with 0.3-mm customized copings at the cervical third and anatomical design elsewhere for up to 5 years of service. Eighteen participants who required an anterior maxillary crown (n=20) and who had signed a consent form approved by the University of Washington Health Sciences Center Human Subjects Division were enrolled. All preparations were standardized and prepared with an occlusal reduction of 1.5 to 2 mm and an axial reduction of 1 to 1.5 mm with 10 degrees of convergence angle. All finish lines were located on the sound tooth structure. Zirconia copings (Lava; 3M ESPE) were custom designed and milled to a 0.3-mm thickness at the cervical third and with selective thickness elsewhere to support the veneering porcelain. All restorations were luted with self-etching self-adhesive composite resin cement. Recall appointments were at 2 weeks, 6 months, and 12 months, and annually thereafter for 5 years. Modified Ryge criteria were used to assess the clinical fracture measurements, esthetics, marginal discoloration, marginal adaptation, radiographic proximal recurrent caries, and periapical pathoses. Descriptive statistics and 95% confidence intervals were used to describe the number and rate of complications and self-reported satisfaction with the crowns. Twenty crowns with a mean follow-up of 58.7 months were evaluated. All crowns were rated as Alfa for fracture measurements (smooth surface, no fracture/chipping). Twelve crowns were rated esthetically as Romeo (no mismatch in color and shade) and 8 as Sierra (mismatch in color and shade within normal range). Twelve crowns were rated as Alfa (no visible evidence of crevice) and 8 as Bravo (visible evidence of crevice, no penetration of explorer) for marginal integrity. Nineteen were rated as Alfa (no discoloration) and 1 as Bravo

  11. Zirconia-Based Screw-Retained Prostheses Supported by Implants: A Retrospective Study on Technical Complications and Failures.

    Science.gov (United States)

    Worni, Andreas; Kolgeci, Lumni; Rentsch-Kollar, Andrea; Katsoulis, Joannis; Mericske-Stern, Regina

    2015-12-01

    Little information is yet available on zirconia-based prostheses supported by implants. To evaluate technical problems and failures of implant-supported zirconia-based prostheses with exclusive screw-retention. Consecutive patients received screw-retained zirconia-based prostheses supported by implants and were followed over a time period of 5 years. The implant placement and prosthetic rehabilitation were performed in one clinical setting, and all patients participated in the maintenance program. The treatment comprised single crowns (SCs) and fixed dental prostheses (FDPs) of three to 12 units. Screw-retention of the CAD/CAM-fabricated SCs and FDPs was performed with direct connection at the implant level. The primary outcome was the complete failure of zirconia-based prostheses; outcome measures were fracture of the framework or extensive chipping resulting in the need for refabrication. A life table analysis was performed, the cumulative survival rate (CSR) calculated, and a Kaplan-Meier curve drawn. Two hundred and ninety-four implants supported 156 zirconia-based prostheses in 95 patients (52 men, 43 women, average age 59.1 ± 11.7 years). Sixty-five SCs and 91 FDPs were identified, comprising a total of 441 units. Fractures of the zirconia framework and extensive chipping resulted in refabrication of nine prostheses. Nearly all the prostheses (94.2%) remained in situ during the observation period. The 5-year CSR was 90.5%, and 41 prostheses (14 SCs, 27 FDPs) comprising 113 units survived for an observation time of more than 5 years. Six SCs exhibited screw loosening, and polishing of minor chipping was required for five prostheses. This study shows that zirconia-based implant-supported fixed prostheses exhibit satisfactory treatment outcomes and that screw-retention directly at the implant level is feasible. © 2014 Wiley Periodicals, Inc.

  12. Marginal and Internal Discrepancies of Posterior Zirconia-Based Crowns Fabricated with Three Different CAD/CAM Systems Versus Metal-Ceramic.

    Science.gov (United States)

    Ortega, Rocio; Gonzalo, Esther; Gomez-Polo, Miguel; Suárez, María J

    2015-01-01

    The aim of this study was to analyze the marginal and internal fit of metalceramic and zirconia-based crowns. Forty standardized steel specimens were prepared to receive posterior crowns and randomly divided into four groups (n = 10): (1) metal-ceramic, (2) NobelProcera Zirconia, (3) Lava Zirconia, and (4) VITA In-Ceram YZ. All crowns were cemented with glass-ionomer agent and sectioned buccolingually. A scanning electron microscope was used for measurements. Kruskal-Wallis and Wilcoxon signed rank test (α = .05) statistical analyses were conducted. Significant differences (P zirconia groups. No differences were found for the axial wall fit (P = .057). Significant differences were shown among the groups in discrepancies at the occlusal cusp (P = .0012) and at the fossa (P = .0062). No differences were observed between surfaces. All zirconia groups showed better values of marginal discrepancies than the metal-ceramic group. Procera Zirconia showed the lowest gaps.

  13. The clinical success of zirconia-based crowns: a systematic review.

    Science.gov (United States)

    Larsson, Christel; Wennerberg, Ann

    2014-01-01

    This review aimed to evaluate the documented clinical success of zirconia based crowns in clinical trials. Electronic databases were searched for original studies reporting on the clinical performance of tooth- or implant-supported zirconia-based crowns, including PubMed, Cochrane Library, and Science Direct. The electronic search was complemented by manual searches of the bibliographies of all retrieved full-text articles and reviews as well as a hand search of the following journals: International Journal of Prosthodontics, Journal of Oral Rehabilitation, International Journal of Oral & Maxillofacial Implants, and Clinical Oral Implants Research. The search yielded 3,216 titles. Based on preestablished criteria, 42 full-text articles were obtained. While 16 studies fulfilled the inclusion criteria, only 3 randomized controlled trials were reported. Seven studies reported on tooth-supported and 4 on implant-supported crowns, and 5 studies reported on both types of support. Ten studies on tooth-supported and 7 on implant supported crowns provided sufficient material for statistical analysis. Life table analysis revealed cumulative 5-year survival rates of 95.9% for tooth-supported and 97.1% for implant-supported crowns. For implant-supported crowns, the most common reasons for failure were technical (veneering material fractures). For tooth-supported crowns, technical (veneering material fractures, loss of retention) and biologic (endodontic/ periodontic) reasons for failure were equally common. The most common complications for implant-supported crowns were veneering material fractures and bleeding on probing. For tooth-supported crowns, the most common complications were loss of retention, endodontic treatment, veneering material fractures, and bleeding on probing. The results suggest that the success rate of tooth-supported and implant-supported zirconia-based crowns is adequate, similar, and comparable to that of conventional porcelain-fused-to-metal crowns

  14. Strength, fracture toughness and microstructure of a selection of all-ceramic materials. Part II. Zirconia-based dental ceramics.

    Science.gov (United States)

    Guazzato, Massimiliano; Albakry, Mohammad; Ringer, Simon P; Swain, Michael V

    2004-06-01

    The present study is the second part of an investigation of strength, fracture toughness and microstructure of nine all-ceramic materials. In the present study, DC Zirkon, an experimental yttria partially stabilized zirconia, In-Ceram Zirconia slip and In-Ceram Zirconia dry-pressed were compared. Strength was appraised on ten bar-shaped specimens for each material (20 x 4 x 1.2 mm) with the three-point bending method. The fracture toughness (Indentation Strength) was measured on twenty specimens (20 x 4 x 2 mm) for each ceramic. The volume fraction of each phase, the dimensions and shapes of the grains and the crack pattern were investigated with SEM. Phase transformation was investigated with X-ray diffraction. Data were compared with an ANOVA and Sheffé post hoc test (p = 0.05). Means of strength (MPa) and fracture toughness (MPa m(1/2)) values and their standard deviation were: In-Ceram Zirconia dry-pressed 476 (50)1, 4.9 (0.36)1; In-Ceram Zirconia slip 630 (58)2, 4.8 (0.50)1; the experimental yttria partially stabilized zirconia 680 (130)2, 5.5 (0.34)2; DC-Zirkon 840 (140)3, 7.4 (0.62)3. Values with the same superscript number showed no significant statistical difference. Microscope investigation and X-ray diffraction revealed the important role played by the tetragonal to monoclinic phase transformation and by the relationship between the glassy matrix and the crystalline phase in the strengthening and toughening mechanisms of these ceramics. the zirconia-based dental ceramics are stronger and tougher materials than the conventional glass-ceramics. Better properties can have positive influence on the clinical performance of all-ceramic restorations. Copyright 2003 Academy of Dental Materials

  15. The use of MDP-based materials for bonding to zirconia.

    Science.gov (United States)

    de Souza, Grace; Hennig, Diana; Aggarwal, Anuj; Tam, Laura E

    2014-10-01

    A strong and stable bond between the luting resin and overlying ceramic restoration is critical to longevity, but no technique has been established for how to provide such a bond when the core material is zirconia. The purpose of this study was to evaluate the effect of different materials containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) on the bond strength to yttria-tetragonal zirconia polycrystal (Y-TZP) ceramic. Forty Y-TZP slices (Lava) were cemented to substrates (8 groups; n=5 in each) with or without the previous application of an experimental primer (0.5% MDP) or an MDP-based adhesive (Clearfil S3 Bond Plus or Scotchbond Universal) with either an MDP (Clearfil SA) or a non-MDP (RelyX Ultimate) luting resin. Specimens were cut, stored in distilled water, and microtensile tested (5 beams per specimen) at 48 hours and again at 6 months after luting procedures. The data were analyzed by 4-way ANOVA (α=.05) and the Tukey test (α=.05). The mode of failure was classified with a stereomicroscope, and the treated surfaces were analyzed with energy-dispersive x-ray spectroscopy. Both adhesive (PMDP-containing adhesive and the shorter storage time were associated with higher bond strengths. At 48 hours, an overall incidence of 50.5% of Type 1 mode of failure (adhesive at ceramic/resin interface) occurred, as opposed to 68% after 6 months of water storage. Energy-dispersive x-ray spectroscopy results showed peaks of carbon and phosphorus when MDP-based materials were used. The application of an MDP-based adhesive may improve bond strength to zirconia. However, microtensile bond strength results for all groups did not remain stable over 6 months. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  16. Zirconia in biomedical applications.

    Science.gov (United States)

    Chen, Yen-Wei; Moussi, Joelle; Drury, Jeanie L; Wataha, John C

    2016-10-01

    The use of zirconia in medicine and dentistry has rapidly expanded over the past decade, driven by its advantageous physical, biological, esthetic, and corrosion properties. Zirconia orthopedic hip replacements have shown superior wear-resistance over other systems; however, risk of catastrophic fracture remains a concern. In dentistry, zirconia has been widely adopted for endosseous implants, implant abutments, and all-ceramic crowns. Because of an increasing demand for esthetically pleasing dental restorations, zirconia-based ceramic restorations have become one of the dominant restorative choices. Areas covered: This review provides an updated overview of the applications of zirconia in medicine and dentistry with a focus on dental applications. The MEDLINE electronic database (via PubMed) was searched, and relevant original and review articles from 2010 to 2016 were included. Expert commentary: Recent data suggest that zirconia performs favorably in both orthopedic and dental applications, but quality long-term clinical data remain scarce. Concerns about the effects of wear, crystalline degradation, crack propagation, and catastrophic fracture are still debated. The future of zirconia in biomedical applications will depend on the generation of these data to resolve concerns.

  17. Effect of the shades of background substructures on the overall color of zirconia-based all-ceramic crowns

    OpenAIRE

    Suputtamongkol, Kallaya; Tulapornchai, Chantana; Mamani, Jatuphol; Kamchatphai, Wannaporn; Thongpun, Noparat

    2013-01-01

    PURPOSE The objective of this study was to determine the effect of the color of a background substructure on the overall color of a zirconia-based all-ceramic crown. MATERIALS AND METHODS Twenty one posterior zirconia crowns were made for twenty subjects. Seven premolar crowns and six molar crowns were cemented onto abutments with metal post and core in the first and second group. In the third group, eight molar crowns were cemented onto abutments with a prefabricated post and composite core ...

  18. Towards long lasting zirconia-based composites for dental implants: Transformation induced plasticity and its consequence on ceramic reliability.

    Science.gov (United States)

    Reveron, Helen; Fornabaio, Marta; Palmero, Paola; Fürderer, Tobias; Adolfsson, Erik; Lughi, Vanni; Bonifacio, Alois; Sergo, Valter; Montanaro, Laura; Chevalier, Jérôme

    2017-01-15

    Zirconia-based composites were developed through an innovative processing route able to tune compositional and microstructural features very precisely. Fully-dense ceria-stabilized zirconia ceramics (84vol% Ce-TZP) containing equiaxed alumina (8vol%Al 2 O 3 ) and elongated strontium hexa-aluminate (8vol% SrAl 12 O 19 ) second phases were obtained by conventional sintering. This work deals with the effect of the zirconia stabilization degree (CeO 2 in the range 10.0-11.5mol%) on the transformability and mechanical properties of Ce-TZP-Al 2 O 3 -SrAl 12 O 19 materials. Vickers hardness, biaxial flexural strength and Single-edge V-notched beam tests revealed a strong influence of ceria content on the mechanical properties. Composites with 11.0mol% CeO 2 or above exhibited the classical behaviour of brittle ceramics, with no apparent plasticity and very low strain to failure. On the contrary, composites with 10.5mol% CeO 2 or less showed large transformation-induced plasticity and almost no dispersion in strength data. Materials with 10.5mol% of ceria showed the highest values in terms of biaxial bending strength (up to 1.1GPa) and fracture toughness (>10MPa√m). In these ceramics, as zirconia transformation precedes failure, the Weibull modulus was exceptionally high and reached a value of 60, which is in the range typically reported for metals. The results achieved demonstrate the high potential of using these new strong, tough and stable zirconia-based composites in structural biomedical applications. Yttria-stabilized (Y-TZP) zirconia ceramics are increasingly used for developing metal-free restorations and dental implants. Despite their success related to their excellent mechanical resistance, Y-TZP can undergo Low Temperature Degradation which could be responsible for restoration damage or even worst the failure of the implant. Current research is focusing on strategies to improve the LTD resistance of Y-TZP or to develop alternative composites with better

  19. Effect of framework design on fracture load after thermal cycling and mechanical loading of implant-supported zirconia-based prostheses.

    Science.gov (United States)

    Komine, Futoshi; Kamio, Shingo; Takata, Hiroki; Yagawa, Shogo; Taguchi, Serina; Taguchi, Kohei; Hashiguchi, Akiko; Matsumura, Hideo

    2018-01-30

    This study evaluated the effect of zirconia framework design on fracture load of implant-supported zirconia-based prostheses after thermal cycling and mechanical loading. Three different zirconia framework designs were investigated: uniform-thickness (UNI), anatomic (ANA), and supported anatomic (SUP) designs. Each framework was layered with feldspathic porcelain (ZAC group) or indirect composite material (ZIC group). The specimens then underwent fracture load testing after thermal cycling and cyclic loading. In the ZAC group, mean fracture load was significantly lower for UNI design specimens than for the other framework designs. In the ZIC group, there was no significant difference in mean fracture load between ANA design specimens and either UNI or SUP design specimens. To improve fracture resistance of implant-supported zirconia-based prostheses after artificial aging, uniformly thick layering material and appropriate lingual support with zirconia frameworks should be provided.

  20. Hydrothermal synthesis and characterization of zirconia based catalysts

    Science.gov (United States)

    Caillot, T.; Salama, Z.; Chanut, N.; Cadete Santos Aires, F. J.; Bennici, S.; Auroux, A.

    2013-07-01

    In this work, three equimolar mixed oxides ZrO2/CeO2, ZrO2/TiO2, ZrO2/La2O3 and a reference ZrO2 have been synthesized by hydrothermal method. The structural and surface properties of these materials have been fully characterized by X-ray diffraction, transmission electron microscopy, surface area measurement, chemical analysis, XPS, infrared spectroscopy after adsorption of pyridine and adsorption microcalorimetry of NH3 and SO2 probe molecules. All investigated mixed oxides are amphoteric and possess redox centers on their surface. Moreover, hydrothermal synthesis leads to catalysts with higher surface area and with better acid-base properties than classical coprecipitation method. Both Lewis and Brønsted acid sites are present on the surface of the mixed oxides. Compared to the other samples, the ZrO2/TiO2 material appears to be the best candidate for further application in acid-base catalysis.

  1. Transmutation of americium and curium incorporated in zirconia-based host materials

    Energy Technology Data Exchange (ETDEWEB)

    Raison, P.E. [CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. d' Etudes des Combustibles; Haire, R.G. [Oak Ridge National Lab., TN (United States)

    2001-07-01

    Presented are studies involving the incorporation of americium and curium in zirconia-based materials. First explored was the pseudo ternary system AmO{sub 2}-ZrO{sub 2}-Y{sub 2}O{sub 3}. It was determined that selected Y-CSZ materials can incorporate significant quantities of americium oxide and remain cubic single-phase. The cell parameters of these fluorite-type products were established to be linear with the AmO{sub 2} content. The Cm{sub 2}O{sub 3}-ZrO{sub 2} system was also investigated. It was found that at 25 mol% of CmO{sub 1.5}, the Cm(III) stabilized zirconia in its cubic form (a = 5.21 {+-}0.01 Angstrom). At higher and lower concentrations, diphasic materials were encountered. At 50 mol% of CmO{sub 1.5}, a pyrochlore oxide - Cm{sub 2}Zr{sub 2}O{sub 7} - is formed (a = 10.63 {+-}0.02 Angstrom). (author)

  2. Shear Bond Strength of Porcelain to a Base-Metal Compared to Zirconia Core

    OpenAIRE

    Abrisham, SM.; Fallah Tafti, A.; Kheirkhah, S.; Tavakkoli, MA.

    2017-01-01

    Statement of Problem: Recent clinical results for Zirconia all-ceramic restorations have revealed that the fracture rate 6-15% of the Zirconia framework is so low and the core of Zirconia has high stability. However, chipping-off fractures of porcelain are the most common reason for failures of Zirconia in the fixed partial dentures. Objectives: The purpose of this study was to compare the shear bond strength (SBS) of porcelain in the porcelain fused to metal and all-ceramic crowns with Z...

  3. Reliability of metalloceramic and zirconia-based ceramic crowns.

    Science.gov (United States)

    Silva, N R F A; Bonfante, E A; Zavanelli, R A; Thompson, V P; Ferencz, J L; Coelho, P G

    2010-10-01

    Despite the increasing utilization of all-ceramic crown systems, their mechanical performance relative to that of metal ceramic restorations (MCR) has yet to be determined. This investigation tested the hypothesis that MCR present higher reliability over two Y-TZP all-ceramic crown systems under mouth-motion fatigue conditions. A CAD-based tooth preparation with the average dimensions of a mandibular first molar was used as a master die to fabricate all restorations. One 0.5-mm Pd-Ag and two Y-TZP system cores were veneered with 1.5 mm porcelain. Crowns were cemented onto aged (60 days in water) composite (Z100, 3M/ESPE) reproductions of the die. Mouth-motion fatigue was performed, and use level probability Weibull curves were determined. Failure modes of all systems included chipping or fracture of the porcelain veneer initiating at the indentation site. Fatigue was an acceleration factor for all-ceramic systems, but not for the MCR system. The latter presented significantly higher reliability under mouth-motion cyclic mechanical testing.

  4. Reliability of Metalloceramic and Zirconia-based Ceramic Crowns

    Science.gov (United States)

    Silva, N.R.F.A.; Bonfante, E.A.; Zavanelli, R.A.; Thompson, V.P.; Ferencz, J.L.; Coelho, P.G.

    2010-01-01

    Despite the increasing utilization of all-ceramic crown systems, their mechanical performance relative to that of metal ceramic restorations (MCR) has yet to be determined. This investigation tested the hypothesis that MCR present higher reliability over two Y-TZP all-ceramic crown systems under mouth-motion fatigue conditions. A CAD-based tooth preparation with the average dimensions of a mandibular first molar was used as a master die to fabricate all restorations. One 0.5-mm Pd-Ag and two Y-TZP system cores were veneered with 1.5 mm porcelain. Crowns were cemented onto aged (60 days in water) composite (Z100, 3M/ESPE) reproductions of the die. Mouth-motion fatigue was performed, and use level probability Weibull curves were determined. Failure modes of all systems included chipping or fracture of the porcelain veneer initiating at the indentation site. Fatigue was an acceleration factor for all-ceramic systems, but not for the MCR system. The latter presented significantly higher reliability under mouth-motion cyclic mechanical testing. PMID:20660796

  5. Influence of CAD/CAM systems and cement selection on marginal discrepancy of zirconia-based ceramic crowns.

    Science.gov (United States)

    Martínez-Rus, Francisco; Suárez, María J; Rivera, Begoña; Pradíes, Guillermo

    2012-04-01

    To analyze the effect of ceramic manufacturing technique and luting cement selection on the marginal adaptation of zirconium oxide-based all-ceramic crowns. An extracted mandibular first premolar was prepared for a complete coverage restoration and subsequently duplicated 40 times in a liquid crystal polymer (LCP). All-ceramic crowns (n = 10) were fabricated on LCP models using the following systems: glass-infiltrated zirconia-toughened alumina (In-Ceram Zirconia) and yttrium cation-doped tetragonal zirconia polycrystals (In-Ceram YZ, Cercon, and Procera Zirconia). The restorations (n = 5) were cemented on their respective dies with glass-ionomer cement (Ketac Cem Aplicap) and resin cement (Panavia 21). The absolute marginal discrepancy of the crowns was measured before and after cementation by scanning electronic microscopy at 160 points along the circumferential margin. The data were analyzed using one-way ANOVA for repeated measures and for independent samples, Scheffé's multiple range post hoc test, and Student's t-test (alpha = 0.05). There were statistical differences in the mean marginal openings among the four all-ceramic systems before and after luting (P cementation values (P cement resulted in larger marginal discrepancies than glass-ionomer cement (P < 0.0001).

  6. Zirconia- versus metal-based, implant-supported abutments and crowns

    DEFF Research Database (Denmark)

    Hosseini, Mandana

    was to test the reliability and validity of six aesthetic parameters used at the Copenhagen Dental School to assess the aesthetic outcome of implant-supported restorations. The aims of study III and IV were to compare the influence of different abutment and crown materials on biological, biomechanical......To restore oral functions in patients with missing teeth, single-tooth implants are a well-documented treatment option. Along with high survival rates, aesthetic factors have become an important clinical outcome variable for evaluating treatment success of implant-supported restorations. Thus...... studies have reported on aesthetic, biological, biomechanical and patient-reported outcomes of implant-supported single-tooth restorations of various biomaterials. The aim of the present thesis was to investigate the clinical performance of zirconia-based implant-supported single-tooth restorations...

  7. A 3 years retrospective study of survival for zirconia-based single crowns fabricated from intraoral digital impressions.

    Science.gov (United States)

    Gherlone, Enrico; Mandelli, Federico; Capparè, Paolo; Pantaleo, Giuseppe; Traini, Tonino; Ferrini, Francesco

    2014-09-01

    To evaluate the clinical performance of glass-ceramic/zirconia crowns fabricated using intraoral digital impressions - a retrospective study with a three-year follow-up. 70 consecutive patients with a total of 86 glass-ceramic/zirconia crowns were treated by a single clinician using standardized clinical and laboratory protocols. A complete digital workflow was adopted for the purpose except for the veneering procedure for the glass-ceramic crowns. Occlusal adjustments were made before the ceramic glazing procedure. Before cementation, all abutments where carefully cleaned with a 70% alcoholic solution and air dried. Cementation was performed using dual-curing, self-adhesive resin cement. Patients were re-examined after 12, 24 and 36 months, to assess crown chipping/fractures. After the three-year follow-up, none of the zirconia-based restoration was lost ("apparent" survival rate 100%) otherwise, the chipping rate of the veneering material increased from 9.3% after 12 months, to 14% after 24 months to 30.2% after 36 months. As a consequence, the "real" success rate after 3 years was 69.8%. After 3 years the success rate of zirconia-based crowns was 69.8%, while the incidence of the chipping was 30.2%. Assuming an exponential increase in chipping rate between 12 and 36 months it can be argued that, among others, the fatigue-mechanism could be advocated as the main factor for the failure of glass-ceramic veneered zirconia especially after 24 months. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Fracture Strength of Aged Monolithic and Bilayer Zirconia-Based Crowns.

    Science.gov (United States)

    Lameira, Deborah Pacheco; Buarque e Silva, Wilkens Aurélio; Andrade e Silva, Frederico; De Souza, Grace M

    2015-01-01

    The purpose of this study was to evaluate the effect of design and surface finishing on fracture strength of yttria-tetragonal zirconia polycrystal (Y-TZP) crowns in monolithic (1.5 mm thickness) and bilayer (0.8 mm zirconia coping and 0.7 mm porcelain veneer) configuration after artificial aging. Bovine incisors received crown preparation and Y-TZP crowns were manufactured using CAD/CAM technique, according to the following groups (n = 10): Polished monolithic zirconia crowns (PM); Glazed monolithic zirconia crowns (GM); Bi-layer crowns (BL). Crowns were cemented with resin cement, submitted to artificial aging in a chewing simulator (2.5 million cycles/80 N/artificial saliva/37 °C), and tested for fracture strength. Two remaining crowns referring to PM and GM groups were submitted to a chemical composition analysis to measure the level of yttrium after aging. One-way ANOVA and Tukey's test (P = .05) indicated that monolithic zirconia crowns presented similar fracture strength (PM = 3476.2 N ± 791.7; GM = 3561.5 N ± 991.6), which was higher than bilayer crowns (2060.4 N ± 810.6). There was no difference in the yttrium content among the three surfaces evaluated in the monolithic crowns. Thus, monolithic zirconia crowns present higher fracture strength than bilayer veneered zirconia after artificial aging and surface finishing does not affect their fracture strength.

  9. Fracture Strength of Aged Monolithic and Bilayer Zirconia-Based Crowns

    OpenAIRE

    Lameira, Deborah Pacheco; Silva, Wilkens Aur?lio Buarque e; Silva, Frederico Andrade e; De Souza, Grace M.

    2015-01-01

    The purpose of this study was to evaluate the effect of design and surface finishing on fracture strength of yttria-tetragonal zirconia polycrystal (Y-TZP) crowns in monolithic (1.5 mm thickness) and bilayer (0.8 mm zirconia coping and 0.7 mm porcelain veneer) configuration after artificial aging. Bovine incisors received crown preparation and Y-TZP crowns were manufactured using CAD/CAM technique, according to the following groups (n = 10): Polished monolithic zirconia crowns (PM); Glazed mo...

  10. Analysis of tooth preparations for zirconia-based crowns and fixed dental prostheses using stereolithography data sets.

    Science.gov (United States)

    Winkelmeyer, Conrad; Wolfart, Stefan; Marotti, Juliana

    2016-11-01

    Under clinical circumstances, it can be challenging for a dentist to achieve an adequate tooth preparation, which is essential for the long-term success of fixed dental restorations. This is particularly true for zirconia restorations fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM) because of the difficulties involved in the scanning and milling process. The purpose of this retrospective study was to use a digital approach to evaluate dental tooth preparations for zirconia-based crowns and fixed dental prostheses (FDP) performed by general dental practitioners in Germany and to find out whether the type of prepared tooth or the type of restoration influenced the outcome. Stereolithography data sets of 182 zirconia frameworks with a total of 305 abutment teeth obtained by the CAD-CAM process were analyzed regarding total occlusal convergence, abutment height, and finish line design using a 3-dimensional (3D) inspection and mesh processing software. The criteria for adequate preparations were defined based on current literature and compared with the measurement results. The Kruskal-Wallis 1-way analysis of variance and the Mann-Whitney U test were applied to detect significant differences (α=.05). Only 13 teeth (4.3%) met the clinical requirements for adequate zirconia-based tooth preparations. The mean total occlusal convergence was 17.9 ±9.7 degrees. Molars (23.2 ±10.1 degrees) showed statistically significant difference (Pcrown and FDP preparations. The mean abutment height was 5.6 ±1.3 mm. Again, significant differences occurred when tooth types (4.8 ±1.0 mm for molars, 5.2 ±0.9 mm for premolars and 6.9 ±1.2 mm for anterior teeth; P≤.01) were compared. In 92.5% of teeth, the finish line design was not ideal for zirconia-based restorations. The tooth preparations of general dental practitioners differ from the ideal clinical preparation recommended for zirconia-based restorations. Difficulties are primarily related to the

  11. Comparative evaluation of shear bond strengths of veneering porcelain to base metal alloy and zirconia substructures before and after aging – An in vitro study

    Science.gov (United States)

    Sreekala, Laju; Narayanan, Mahesh; Eerali, Sunil M.; Eerali, Susil M.; Varghese, Joju; Zainaba Fathima, A. l.

    2015-01-01

    Objective: The aim of this study was to evaluate and compare the shear bond strength of veneering porcelain to base metal alloy and zirconia substructures before and after aging. Scanning electron microscopy (SEM) was used to determine the failure pattern. Materials and Methods: Twenty rectangular blocks (9 mm length × 4 mm height × 4 mm width) of base metal alloy (Bellabond plus, Bego, Germany) and zirconia (Will ceramZ zirconia K block) were fabricated for shear bond strength test. Surface of the base metal alloy block (4 mm × 4 mm area) was veneered with corresponding veneering porcelain (Ivoclar, IPS classic, vivadent). Similarly, surface of the zirconia rectangular block (4 mm × 4 mm) was veneered with corresponding veneering ceramic (Cercon ceram kiss, Degudent). Out of forty rectangular porcelain veneered core specimen, ten porcelain veneered base metal alloy specimen and ten porcelain veneered zirconia specimen were immersed in water at 37°C for one month to simulate the oral environment. Results: On comparison, the highest shear bond strength value was obtained in porcelain veneered base metal alloy before aging group followed by porcelain veneered base metal alloy after aging group, Porcelain veneered zirconia before aging group, porcelain veneered zirconia after aging group. SEM analysis revealed predominantly cohesive failure of veneering ceramic in all groups. Conclusion: Porcelain veneered base metal alloy samples showed highest shear bond strength than porcelain veneered zirconia samples. Study concluded that aging had an influence on shear bond strength. Shear bond strength was found to be decreasing after aging. SEM analysis revealed cohesive failure of veneering ceramic in all groups suggestive of higher bond strength of the interface than cohesive strength of ceramic. Hence, it was concluded that veneering ceramic was the weakest link. PMID:26942121

  12. Comparative evaluation of shear bond strengths of veneering porcelain to base metal alloy and zirconia substructures before and after aging - An in vitro study.

    Science.gov (United States)

    Sreekala, Laju; Narayanan, Mahesh; Eerali, Sunil M; Eerali, Susil M; Varghese, Joju; Zainaba Fathima, A L

    2015-12-01

    The aim of this study was to evaluate and compare the shear bond strength of veneering porcelain to base metal alloy and zirconia substructures before and after aging. Scanning electron microscopy (SEM) was used to determine the failure pattern. Twenty rectangular blocks (9 mm length × 4 mm height × 4 mm width) of base metal alloy (Bellabond plus, Bego, Germany) and zirconia (Will ceramZ zirconia K block) were fabricated for shear bond strength test. Surface of the base metal alloy block (4 mm × 4 mm area) was veneered with corresponding veneering porcelain (Ivoclar, IPS classic, vivadent). Similarly, surface of the zirconia rectangular block (4 mm × 4 mm) was veneered with corresponding veneering ceramic (Cercon ceram kiss, Degudent). Out of forty rectangular porcelain veneered core specimen, ten porcelain veneered base metal alloy specimen and ten porcelain veneered zirconia specimen were immersed in water at 37°C for one month to simulate the oral environment. On comparison, the highest shear bond strength value was obtained in porcelain veneered base metal alloy before aging group followed by porcelain veneered base metal alloy after aging group, Porcelain veneered zirconia before aging group, porcelain veneered zirconia after aging group. SEM analysis revealed predominantly cohesive failure of veneering ceramic in all groups. Porcelain veneered base metal alloy samples showed highest shear bond strength than porcelain veneered zirconia samples. Study concluded that aging had an influence on shear bond strength. Shear bond strength was found to be decreasing after aging. SEM analysis revealed cohesive failure of veneering ceramic in all groups suggestive of higher bond strength of the interface than cohesive strength of ceramic. Hence, it was concluded that veneering ceramic was the weakest link.

  13. Fracture resistance of zirconia-composite veneered crowns in comparison with zirconia-porcelain crowns.

    Science.gov (United States)

    Alsadon, Omar; Patrick, David; Johnson, Anthony; Pollington, Sarah; Wood, Duncan

    2017-05-31

    The objectives were to evaluate the fracture resistance and stress concentration in zirconia/composite veneered crowns in comparison to zirconia/porcelain crowns using occlusal fracture resistance and by stress analysis using finite element analysis method. Zirconia substructures were divided into two groups based on the veneering material. A static load was applied occlusally using a ball indenter and the load to fracture was recorded in Newtons (N). The same crown design was used to create 3D crown models and evaluated using FEA. The zirconia/composite crowns subjected to static occlusal load showed comparable results to the zirconia/porcelain crowns. Zirconia/composite crowns showed higher stress on the zirconia substructure at 63.6 and 50.9 MPa on the zirconia substructure veneered with porcelain. In conclusion, zirconia/composite crowns withstood high occlusal loads similar to zirconia/porcelain crowns with no significant difference. However, the zirconia/composite crowns showed higher stress values than the zirconia/porcelain crowns at the zirconia substructure.

  14. Methanol synthesis from CO2 hydrogenation over Cu based catalyst supported on zirconia modified γ-Al2O3

    International Nuclear Information System (INIS)

    Zhang Yiping; Fei Jinhua; Yu Yingmin; Zheng Xiaoming

    2006-01-01

    The effect of zirconia modification on γ-Al 2 O 3 support to the Cu based catalyst was studied. It is found that the catalytic activity and methanol selectivity of the catalyst after Zr addition are both improved. The influences of reaction temperature, space velocity and the molar ratio of H 2 :CO 2 on Cu/γ-Al 2 O 3 and 12Cu10Zr/γ-Al 2 O 3 catalyst were also studied. The results indicate that low temperature, high space velocity and proper molar ratio of H 2 /CO 2 are advantageous to methanol synthesis. The XRD and TPR characterization show that the addition of Zr enhances the dispersion of CuO species, which is responsible for the enhanced catalytic performance of Cu based catalyst supported on zirconia modified γ-Al 2 O 3 catalyst

  15. Bonding of resin-based luting cements to zirconia with and without the use of ceramic priming agents.

    Science.gov (United States)

    Koizumi, Hiroyasu; Nakayama, Daisuke; Komine, Futoshi; Blatz, Markus B; Matsumura, Hideo

    2012-08-01

    This study evaluated and compared bonding characteristics of resin-based luting agents and special ceramic primers to zirconia. Disk specimens (n = 242) were fabricated from zirconium dioxide ceramics (Katana) and bonded with four resin-based luting agents without priming. In addition, zirconia was bonded with 7 bondingsystem combinations of three priming agents and three resin-based luting agents. Two of the resin-based luting agents and two ceramic priming agents contain an identical adhesive monomer, 10-methacryloyloxydecyl dihydrogen phosphate (MDP), either in the material itself or in the priming agent. Shear bond strength was determined after 20,000 cycles of thermocycling. The Kruskal-Wallis test was performed for both pre- and post-thermocycling groups to evaluate the difference among primer and luting agent variations. On the basis of the Kruskal-Wallis test, Steel-Dwass multiple comparisons were further performed to compare the difference among four luting agents and seven conbinations of three primers and three luting agents for both pre- and post-thermocycling conditions. Within the four unprimed groups, Clearfil SA Cement (5.8 MPa) and Panavia F 2.0 (6.7 MPa) showed statistically higher post-thermocycling bond strength than the other materials (0.1 MPa) (p primed with Monobond Plus (4.0-4.6 MPa) (p priming agents containing the adhesive monomer MDP provide better bond strength to zirconia than do other systems.

  16. Clinical evaluation of zirconia-based all-ceramic single crowns: an up to 12-year retrospective cohort study.

    Science.gov (United States)

    Miura, Shoko; Kasahara, Shin; Yamauchi, Shinobu; Okuyama, Yayoi; Izumida, Akio; Aida, Jun; Egusa, Hiroshi

    2018-03-01

    This study aims to investigate the incidence of clinical complications with tooth-supported zirconia-based all-ceramic single crowns and identify pertinent risk parameters. A retrospective cohort study (May 2004 to April 2016) utilizing clinical records of patients receiving yttrium-oxide-partially stabilized zirconia (Y-TZP)-based all-ceramic crowns placed at Tohoku University Hospital was performed. The length of time of treatment success (complication event-free) and restoration survival (including minor complication events and remaining clinically functional) were estimated using Kaplan-Meier analysis. Multilevel survival analysis was used to identify risk factors. One hundred thirty-seven crowns were evaluated (mean follow-up time, 7.0 years). A total of 21 crowns experienced at least one complication with fracture of veneering ceramic being the most common (16 crowns). Estimated success and survival rates at 5 years (96.9 and 98.5%, respectively) decreased at 10 years to 62.1 and 67.2%, respectively. The risk of complications was significantly higher for molar crowns compared to anterior crowns (p crowns placed on anterior teeth demonstrated encouraging clinical results over a period of up to 10 years. However, there is a substantial risk of complications with posterior teeth within 10 years of restoration placement. Treatment with zirconia-based all-ceramic crowns for molar teeth with metal antagonist occlusion should be undertaken with caution.

  17. Zirconia-based dental crown to support a removable partial denture: a three-dimensional finite element analysis using contact elements and micro-CT data.

    Science.gov (United States)

    Rocha, Eduardo Passos; Anchieta, Rodolfo Bruniera; de Almeida, Erika Oliveira; Freitas, Amilcar Chagas; Martini, Ana Paula; Sotto-Maior, Bruno Sales; Luersen, Marco Antonio; Ko, Ching Chang

    2015-01-01

    Veneer fracture is the most common complication in zirconia-based restorations. The aim of this study was to evaluate the mechanical behavior of a zirconia-based crown in a lower canine tooth supporting removable partial denture (RPD) prosthesis, varying the bond quality of the veneer/coping interface. Microtomography (μCT) data of an extracted left lower canine were used to build the finite element model (M) varying the core material (gold core - MAu; zirconia core - MZi) and the quality of the veneer/core interface (complete bonded - MZi; incomplete bonded - MZi-NL). The incomplete bonding condition was only applied for zirconia coping by using contact elements (Target/Contact) with 0.3 frictional coefficients. Stress fields were obtained using Ansys Workbench 10.0. The loading condition (L = 1 N) was vertically applied at the base of the RPD prosthesis metallic support towards the dental apex. Maximum principal (σmax) and von Mises equivalent (σvM) stresses were obtained. The σmax (MPa) for the bonded condition was similar between gold and zirconia cores (MAu, 0.42; MZi, 0.40). The incomplete bonded condition (MZi-NL) raised σmax in the veneer up to 800% (3.23 MPa) in contrast to the bonded condition. The peak of σvM increased up to 270% in the MZi-NL. The incomplete bond condition increasing the stress in the veneer/zirconia interface.

  18. How to Bond Zirconia: The APC Concept.

    Science.gov (United States)

    Blatz, Markus B; Alvarez, Marcela; Sawyer, Kimiyo; Brindis, Marco

    2016-10-01

    Zirconia has become one of the most popular materials in dentistry. New high-translucent zirconia ceramics have favorable optical properties and can be applied as monolithic full-contour restorations in various clinical indications for posterior and anterior teeth. However, having reliable cementation protocols is fundamental for clinical success of indirect ceramic dental restorations, including those made from zirconia materials. Resin bonding supports ceramic restorations and is necessary for onlays, laminate veneers, and resinbonded fixed dental prostheses. The APC zirconia-bonding concept is based on decades of research on how to achieve high and long-term durable bond strengths to high-strength ceramics. It includes three practical steps: (A) airparticle abrasion, (P) zirconia primer, and (C) adhesive composite resin. This article discusses the history and development of high-translucent zirconia and explains the necessity for proper cementation. The rationale and science behind a simplified zirconia-bonding concept is explained and illustrated with a clinical case presentation.

  19. Fracture Strength of Aged Monolithic and Bilayer Zirconia-Based Crowns

    Directory of Open Access Journals (Sweden)

    Deborah Pacheco Lameira

    2015-01-01

    Full Text Available The purpose of this study was to evaluate the effect of design and surface finishing on fracture strength of yttria-tetragonal zirconia polycrystal (Y-TZP crowns in monolithic (1.5 mm thickness and bilayer (0.8 mm zirconia coping and 0.7 mm porcelain veneer configuration after artificial aging. Bovine incisors received crown preparation and Y-TZP crowns were manufactured using CAD/CAM technique, according to the following groups (n=10: Polished monolithic zirconia crowns (PM; Glazed monolithic zirconia crowns (GM; Bi-layer crowns (BL. Crowns were cemented with resin cement, submitted to artificial aging in a chewing simulator (2.5 million cycles/80 N/artificial saliva/37°C, and tested for fracture strength. Two remaining crowns referring to PM and GM groups were submitted to a chemical composition analysis to measure the level of yttrium after aging. One-way ANOVA and Tukey’s test (P=.05 indicated that monolithic zirconia crowns presented similar fracture strength (PM=3476.2 N ± 791.7; GM=3561.5 N ± 991.6, which was higher than bilayer crowns (2060.4 N ± 810.6. There was no difference in the yttrium content among the three surfaces evaluated in the monolithic crowns. Thus, monolithic zirconia crowns present higher fracture strength than bilayer veneered zirconia after artificial aging and surface finishing does not affect their fracture strength.

  20. Fracture Strength of Aged Monolithic and Bilayer Zirconia-Based Crowns

    Science.gov (United States)

    Lameira, Deborah Pacheco; Silva, Wilkens Aurélio Buarque e; Silva, Frederico Andrade e; De Souza, Grace M.

    2015-01-01

    The purpose of this study was to evaluate the effect of design and surface finishing on fracture strength of yttria-tetragonal zirconia polycrystal (Y-TZP) crowns in monolithic (1.5 mm thickness) and bilayer (0.8 mm zirconia coping and 0.7 mm porcelain veneer) configuration after artificial aging. Bovine incisors received crown preparation and Y-TZP crowns were manufactured using CAD/CAM technique, according to the following groups (n = 10): Polished monolithic zirconia crowns (PM); Glazed monolithic zirconia crowns (GM); Bi-layer crowns (BL). Crowns were cemented with resin cement, submitted to artificial aging in a chewing simulator (2.5 million cycles/80 N/artificial saliva/37°C), and tested for fracture strength. Two remaining crowns referring to PM and GM groups were submitted to a chemical composition analysis to measure the level of yttrium after aging. One-way ANOVA and Tukey's test (P = .05) indicated that monolithic zirconia crowns presented similar fracture strength (PM = 3476.2 N ± 791.7; GM = 3561.5 N ± 991.6), which was higher than bilayer crowns (2060.4 N ± 810.6). There was no difference in the yttrium content among the three surfaces evaluated in the monolithic crowns. Thus, monolithic zirconia crowns present higher fracture strength than bilayer veneered zirconia after artificial aging and surface finishing does not affect their fracture strength. PMID:26576423

  1. Characterization of zirconia-based slurries with different binders for titanium investment casting

    Directory of Open Access Journals (Sweden)

    Zhao Ertuan

    2012-05-01

    Full Text Available The materials and physical properties of primary slurry are crucial to the surface quality of the finished castings, especially for high reactivity titanium alloys. The aim of this study is to investigate the influence of different binders on the physical properties of primary slurry for titanium alloy investment casting. The zirconia-based slurries with different binders were evaluated by comparing the parameters: viscosity, bulk density, plate weight, suspensibility, gel velocity and strength. The results indicate that a higher viscosity of binder leads to a higher viscosity and suspensibility of slurry with the same powder/binder ratio. The retention rate and thickness of primary layer increase with an increase in the viscosity of the slurry, and a higher retention rate is associated with a thicker primary layer. The gel velocity of the slurry is correlated with the gel velocity of the binder. The green strength and the baked strength of the primary layer are determined by the properties of the binder after gel and by the production of the binder after fired, respectively.

  2. Effects of silane- and MDP-based primers application orders on zirconia-resin adhesion-A ToF-SIMS study.

    Science.gov (United States)

    Chuang, Shu-Fen; Kang, Li-Li; Liu, Yi-Chuan; Lin, Jui-Che; Wang, Ching-Cheng; Chen, Hui-Min; Tai, Cheng-Kun

    2017-08-01

    To evaluate the 3-methacryloyloxypropyltrimethoxysilane (MPS)- and 10-methacryloyloxydecyl-dihydrogen-phosphate (MDP)-base primers, in their single or sequential applications, with regard to modifying zirconia surfaces and improving resin-zirconia adhesion. Zirconia disks received different treatments: without primer (Zr), MPS-base primer (S), MDP-base primer (M), MPS/MDP mixture (SMmix), MPS followed by MDP (SM), and MDP followed by MPS (MS). The compositions and chemical interactions of the coatings to zirconia were analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and reconstructed 3D ion images. Surface wettability of these coatings to water and resin adhesive was assessed. The shear bond strength (SBS) between resin and the treated zirconia was also examined before and after thermocycling. Groups S and MS presented substantial OH - ions in the coatings and zirconia substrate. PO 2 - and PO 3 - fragments existed in all MDP-treatment groups with various proportions and distributions, while groups M and SM showed higher proportions of PO 3 - and the zirconium phosphate related ions. In 3D ion images, PO 3 - in groups M and SM was denser and segregated to the interface, but was dispersed or overlaid above PO 2 - in SMmix and MS. All the primers increased the surface wettability to water and resin, with M and SM presenting superhydrophilic surfaces. All MDP-treatment groups showed improved SBS before thermocycling, while M and SM retained higher SBS after this. The MDP-base primer shows a relevant function in facilitating POZr bonding and enhancing resin-zirconia bonding. The co-treated MPS impairs the chemical activity of MDP, especially if it is the final coat. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  3. Evaluation of the adaptation of zirconia-based fixed partial dentures using micro-CT technology

    Directory of Open Access Journals (Sweden)

    Marcia Borba

    2013-09-01

    Full Text Available The objective of the study was to measure the marginal and internal fit of zirconia-based all-ceramic three-unit fixed partial dentures (FPDs (Y-TZP - LAVA, 3M-ESPE, using a novel methodology based on micro-computed tomography (micro-CT technology. Stainless steel models of prepared abutments were fabricated to design FPDs. Ten frameworks were produced with 9 mm2 connector cross-sections using a LAVATM CAD-CAM system. All FPDs were veneered with a compatible porcelain. Each FPD was seated on the original model and scanned using micro-CT. Files were processed using NRecon and CTAn software. Adobe Photoshop and Image J software were used to analyze the cross-sectional images. Five measuring points were selected, as follows: MG - marginal gap; CA - chamfer area; AW - axial wall; AOT - axio-occlusal transition area; OA - occlusal area. Results were statistically analyzed by Kruskall-Wallis and Tukey's post hoc test (α= 0.05. There were significant differences for the gap width between the measurement points evaluated. MG showed the smallest median gap width (42 µm. OA had the highest median gap dimension (125 µm, followed by the AOT point (105 µm. CA and AW gap width values were statistically similar, 66 and 65 µm respectively. Thus, it was possible to conclude that different levels of adaptation were observed within the FPD, at the different measuring points. In addition, the micro-CT technology seems to be a reliable tool to evaluate the fit of dental restorations.

  4. Evaluation of the adaptation of zirconia-based fixed partial dentures using micro-CT technology

    International Nuclear Information System (INIS)

    Borba, Marcia; Bona, Alvaro Della

    2013-01-01

    The objective of the study was to measure the marginal and internal fit of zirconia-based all-ceramic three-unit fixed partial dentures (FPDs) (Y-TZP - LAVA, 3M-ESPE), using a novel methodology based on micro-computed tomography (micro-CT) technology. Stainless steel models of prepared abutments were fabricated to design FPDs. Ten frameworks were produced with 9 mm² connector cross-sections using a LAVA® CAD-CAM system. All FPDs were veneered with a compatible porcelain. Each FPD was seated on the original model and scanned using micro-CT. Files were processed using NRecon and CTAn software. Adobe Photoshop and Image J software were used to analyze the cross sectional images. Five measuring points were selected, as follows: MG- marginal gap; CA - chamfer area; AW - axial wall; AOT - axio-occlusal transition area; OA - occlusal area. Results were statistically analyzed by Kruskall-Wallis and Tukey's post hoc test (α = 0.05). There were significant differences for the gap width between the measurement points evaluated. MG showed the smallest median gap width (42 μm). OA had the highest median gap dimension (125 μm), followed by the AOT point (105 μm). CA and AW gap width values were statistically similar, 66 and 65 μm respectively. Thus, it was possible to conclude that different levels of adaptation were observed within the FPD, at the different measuring points. In addition, the micro-CT technology seems to be a reliable tool to evaluate the fit of dental restorations. (author)

  5. Evaluation of the adaptation of zirconia-based fixed partial dentures using micro-CT technology

    Energy Technology Data Exchange (ETDEWEB)

    Borba, Marcia; Bona, Alvaro Della, E-mail: marcia_borb@hotmail.com [Universidade de Passo Fundo (UPF), RS (Brazil). Fac. de Odontologia; Miranda Junior, Walter Gomes; Cesar, Paulo Francisco [Universidade de Sao Paulo (USP), SP (Brazil). Fac. de Odontologia. Dept. de Biomateriais e Bioquimica Oral; Griggs, Jason Allan [Department of Biomedical Materials Science, Dental School, University of Mississippi Medical Center - UMMC, Jackson, MS (United States)

    2013-09-15

    The objective of the study was to measure the marginal and internal fit of zirconia-based all-ceramic three-unit fixed partial dentures (FPDs) (Y-TZP - LAVA, 3M-ESPE), using a novel methodology based on micro-computed tomography (micro-CT) technology. Stainless steel models of prepared abutments were fabricated to design FPDs. Ten frameworks were produced with 9 mm² connector cross-sections using a LAVA® CAD-CAM system. All FPDs were veneered with a compatible porcelain. Each FPD was seated on the original model and scanned using micro-CT. Files were processed using NRecon and CTAn software. Adobe Photoshop and Image J software were used to analyze the cross sectional images. Five measuring points were selected, as follows: MG- marginal gap; CA - chamfer area; AW - axial wall; AOT - axio-occlusal transition area; OA - occlusal area. Results were statistically analyzed by Kruskall-Wallis and Tukey's post hoc test (α = 0.05). There were significant differences for the gap width between the measurement points evaluated. MG showed the smallest median gap width (42 μm). OA had the highest median gap dimension (125 μm), followed by the AOT point (105 μm). CA and AW gap width values were statistically similar, 66 and 65 μm respectively. Thus, it was possible to conclude that different levels of adaptation were observed within the FPD, at the different measuring points. In addition, the micro-CT technology seems to be a reliable tool to evaluate the fit of dental restorations. (author)

  6. Estimation of lattice strain for zirconia nanoparticles based on Williamson- Hall analysis

    Energy Technology Data Exchange (ETDEWEB)

    Aly, Kamal A., E-mail: kamalaly2001@gmail.com [Physics Department, Faculty of Science & Arts, Khullais, University of Jeddah, Jeddah (Saudi Arabia); Physics Department, Faculty of Science, Al-Azhar University, Assiut Branch, Assiut (Egypt); Khalil, N.M. [Chemistry Department, Faculty of Science & Arts, Khullais, University of Jeddah, Jeddah (Saudi Arabia); Refractories, Ceramics and Building Materials Department, National Research Centre, 12311, Cairo (Egypt); Algamal, Yousif [Chemistry Department, Faculty of Science & Arts, Khullais, University of Jeddah, Jeddah (Saudi Arabia); Saleem, Qaid M.A. [Chemistry Department, Faculty of Science & Arts, Khullais, University of Jeddah, Jeddah (Saudi Arabia); Aden University, Shabwa (Yemen)

    2017-06-01

    Nanoparticles of Zirconia were prepared (ZrO{sub 2}) by the neutralization of zirconium oxychloride octahydrate (ZrOCl{sub 2}-8H{sub 2}O) (2M) and ammonia solution (2M) at pH 8. The ZrO{sub 2} crystalline state was revealed by X-ray diffraction (XRD). The analysis of Scanning electron microscopy (SEM) and Transmission Electron microscope (TEM) images reveals that the as-synthesized ZrO{sub 2} particles at firing temperature of 800 °C are uniform and of range of 30 nm. Increasing of the temperature up to 1100 °C leads to the increase in particle size and alters the powders shape due to agglomeration arose from zirconia calcination as well as the increase in particle size. The X-ray peak broadening analysis (XRDBA) was used in the estimation of the crystalline size. Williamson-Hall (W-H) analysis was applied successfully to determine the energy density, stress, and the strain values via uniform deformation model (UDM), uniform deformation stress model (UDSM) and uniform deformation energy density model (UDEDM). The mean of the strain root square was calculated. The different strain values obtained from these models predicting the zirconia isotropic behavior. In addition to that, the W-H analysis results were discussed in terms of that obtained by Scherrer’s relationship, SEM and TEM images. - Graphical abstract: XRD patterns for zirconia nano-particles at different calcined temperature. - Highlights: • Nanoparticles of Zirconia (ZrO{sub 2}) were synthesized. • The ZrO{sub 2} crystalline state was revealed by XRD, SEM and TEM. • SEM and TEM images reveals that the ZrO{sub 2} particles are uniform and relatively small. • Both blocky particles and the powders shape are affected by the firing temperature. • The crystalline sizes were estimated using X-ray peak broadening analysis (XRDBA).

  7. A study of the Lewis acid-base interactions of vinylphosphonic acid-modified polybutadiene-coated zirconia.

    Science.gov (United States)

    Trammell, B C; Hillmyer, M A; Carr, P W

    2001-07-15

    Polybutadiene-coated zirconia (PBD-ZrO2) is very useful for reversed-phase separations under a wide variety of conditions. Its excellent chemical (pH = 1-13) and thermal (up to 150 degrees C) stability distinguish it from silica-based reversed phases. Just as with silica-based phases, zirconia's surface chemistry significantly influences the chromatography of certain classes of analytes. Zirconia's hard Lewis acid sites can be chromatographically problematic. Analytes such as carboxylic acids strongly interact with these sites on PBD-ZrO2 and do not elute. Addition of phosphate or other strong, hard Lewis bases to the eluent brings about elution, but the resulting peak is often tailed and broad. Typically, cationic solutes are more retained in the presence of phosphate or fluoride due to adsorption of the Lewis base additives and the concomitant development of a negative charge on the surface. This Coulombic interaction can be used to optimize selectivity, but the reversed-phase-cation-exchange retention can produce broad peaks with excessive retention. As an alternative to adding Lewis bases to the eluent, we studied the effect of permanently modifying PBD-ZrO2 by covalently attaching vinylphosphonic acid (VPA) to PBD which was predeposited in the pores of zirconia. We have investigated the chromatography of acids, bases, and small peptides on VPA-modified PBD-ZrO2 (VPA-PBD-ZrO2) and compared it to PBD-ZrO2. VPA-PBD-ZrO2 is a reversed-cation-exchange phase with properties quite different from PBD-ZrO2. The chemical stability of both phases led us to explore how low-pH (1.5-3), ultralow-pH (0), and high-pH (12) eluents effect the retention properties of these mixed-mode phases. Ultralow-pH eluents effectively separate small peptides on both phases. This approach gives lower retention, without sacrificing resolution, and much higher efficiency for small peptides than previously reported.

  8. Synthesis and ceramic processing of alumina and zirconia based composites infiltrated with glass phase for dental applications; Sintese e processamento de compositos a base de alumina e zirconia com infiltracao de fase vitrea para aplicacoes odontologicas

    Energy Technology Data Exchange (ETDEWEB)

    Duarte, Daniel Gomes

    2009-07-01

    The interest for the use of ceramic materials for dental applications started due to the good aesthetic appearance promoted by the similarity to natural teeth. However, the fragility of traditional ceramics was a limitation for their use in stress conditions. The development of alumina and zirconia based materials, that associate aesthetic results, biocompatibility and good mechanical behaviour, makes possible the employment of ceramics for fabrication of dental restorations. The incorporation of vitreous phase in these ceramics is an alternative to minimize the ceramic retraction and to improve the adhesion to resin-based cements, necessary for the union of ceramic frameworks to the remaining dental structure. In the dentistry field, alumina and zirconia ceramic infiltrated with glassy phase are represented commercially by the In-Ceram systems. Considering that the improvement of powder's synthesis routes and of techniques of ceramic processing contributes for good performance of these materials, the goal of the present work is the study of processing conditions of alumina and/or 3 mol% yttria-stabilized zirconia ceramics infiltrated with aluminum borosilicate lanthanum glass. The powders, synthesized by hydroxide coprecipitation route, were pressed by uniaxial compaction and pre-sintered at temperature range between 950 and 1650 degree C in order to obtain porous ceramics bodies. Vitreous phase incorporation was performed by impregnation of aluminum borosilicate lanthanum powder, also prepared in this work, followed by heat treatment between 1200 and 1400 degree C .Ceramic powders were characterized by thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, gaseous adsorption (BET) and laser diffraction. Sinterability of alumina and /or stabilized zirconia green pellets was evaluated by dilatometry. Pre-sintered ceramics were characterized by apparent density measurements (Archimedes method), X-ray diffraction and scanning

  9. Shear bond strength of a denture base acrylic resin and gingiva-colored indirect composite material to zirconia ceramics.

    Science.gov (United States)

    Kubochi, Kei; Komine, Futoshi; Fushiki, Ryosuke; Yagawa, Shogo; Mori, Serina; Matsumura, Hideo

    2017-04-01

    To evaluate the shear bond strengths of two gingiva-colored materials (an indirect composite material and a denture base acrylic resin) to zirconia ceramics and determine the effects of surface treatment with various priming agents. A gingiva-colored indirect composite material (CER) or denture base acrylic resin (PAL) was bonded to zirconia disks with unpriming (UP) or one of seven priming agents (n=11 each), namely, Alloy Primer (ALP), Clearfil Photo Bond (CPB), Clearfil Photo Bond with Clearfil Porcelain Bond Activator (CPB+Act), Metal Link (MEL), Meta Fast Bonding Liner (MFB), MR. bond (MRB), and V-Primer (VPR). Shear bond strength was determined before and after 5000 thermocycles. The data were analyzed with the Kruskal-Wallis test and Steel-Dwass test. The mean pre-/post-thermalcycling bond strengths were 1.0-14.1MPa/0.1-12.1MPa for the CER specimen and 0.9-30.2MPa/0.1-11.1MPa for the PAL specimen. For the CER specimen, the ALP, CPB, and CPB+Act groups had significantly higher bond strengths among the eight groups, at both 0 and 5000 thermocycles. For the PAL specimen, shear bond strength was significantly lower after thermalcycling in all groups tested. After 5000 thermocycles, bond strengths were significantly higher in the CPB and CPB+Act groups than in the other groups. For the PAL specimens, bond strengths were significantly lower after thermalcycling in all groups tested. The MDP functional monomer improved bonding of a gingiva-colored indirect composite material and denture base acrylic resin to zirconia ceramics. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  10. Fracture strength of zirconia implant abutments on narrow diameter implants with internal and external implant abutment connections: A study on the titanium resin base concept.

    Science.gov (United States)

    Sailer, Irena; Asgeirsson, Asgeir G; Thoma, Daniel S; Fehmer, Vincent; Aspelund, Thor; Özcan, Mutlu; Pjetursson, Bjarni E

    2018-03-11

    There is limited knowledge regarding the strength of zirconia abutments with internal and external implant abutment connections and zirconia abutments supported by a titanium resin base (Variobase, Straumann) for narrow diameter implants. To compare the fracture strength of narrow diameter abutments with different types of implant abutment connections after chewing simulation. Hundred and twenty identical customized abutments with different materials and implant abutment connections were fabricated for five groups: 1-piece zirconia abutment with internal connection (T1, Cares-abutment-Straumann BL-NC implant, Straumann Switzerland), 1-piece zirconia abutment with external hex connection (T2, Procera abutment-Branemark NP implant, Nobel Biocare, Sweden), 2-piece zirconia abutments with metallic insert for internal connection (T3, Procera abutment-Replace NP implant, Nobel Biocare), 2-piece zirconia abutment on titanium resin base (T4, LavaPlus abutment-VarioBase-Straumann BL-NC implant, 3M ESPE, Germany) and 1-piece titanium abutment with internal connection (C, Cares-abutment-Straumann BL-NC implant, Straumann, Switzerland). All implants had a narrow diameter ranging from 3.3 to 3.5 mm. Sixty un-restored abutments and 60 abutments restored with glass-ceramic crowns were tested. Mean bending moments were compared using ANOVA with p-values adjusted for multiple comparisons using Tukey's procedure. The mean bending moments were 521 ± 33 Ncm (T4), 404 ± 36 Ncm (C), 311 ± 106 Ncm (T1) 265 ± 22 Ncm (T3) and 225 ± 29 (T2) for un-restored abutments and 278 ± 84 Ncm (T4), 302 ± 170 Ncm (C), 190 ± 55 Ncm (T1) 80 ± 102 Ncm (T3) and 125 ± 57 (T2) for restored abutments. For un-restored abutments, C and T4 had similar mean bending moments, significantly higher than those of the three other groups (p < .05). Titanium abutments (C) had significantly higher bending moments than identical zirconia abutments (T1) (p < .05). Zirconia

  11. Marginal fit of alumina-and zirconia-based fixed partial dentures produced by a CAD/CAM system.

    Science.gov (United States)

    Tinschert, J; Natt, G; Mautsch, W; Spiekermann, H; Anusavice, K J

    2001-01-01

    Clinical long-term success of all-ceramic dental restorations can be significantly influenced by marginal discrepancies. As a result, this in vitro study evaluated the marginal fit of alumina- and zirconia-based fixed partial dentures (FPDs) machined by the Precident DCS system. Different master steel models of three-, four- and five-unit posterior FPDs with an 0.8 mm chamfer preparation were produced. FPDs made of DC-Zirkon and In-Ceram Zirconia core ceramics were machined by the Precident DCS system. The marginal fit of the milled frameworks placed on the master steel models was determined by a replica technique using a light-body silicone to fill the discrepancies between crown and tooth and a heavy-body material to stabilize the light-body impression material. The impressions were poured into an epoxy resin material and each model was cross-sectioned with a low speed diamond saw to better visualize marginal discrepancies. The marginal fit of the FPDs was evaluated by scanning electron microscopy. The measurements of the marginal fit exhibited mean marginal discrepancies in a range between 60.5 and 74.0 microm, mean marginal gaps in a range from 42.9 to 46.3 microm, mean vertical discrepancies in a range from 20.9 to 48.0 microm and mean horizontal discrepancies in the range of 42.0 to 58.8 microm. Statistical data analysis was performed using the non-parametric test of Kruskal-Wallis and Mann-Whitney. The analysis revealed no significant differences (p>0.05) between the mean marginal gaps and vertical and horizontal discrepancies. However, for some FPDs the mean values of the marginal discrepancies were significantly different (p zirconia-based FPDs achieved with the Precident DCS system meet the clinical requirements.

  12. Effect of priming agents on shear bond strengths of resin-based luting agents to a translucent zirconia material.

    Science.gov (United States)

    Yagawa, Shogo; Komine, Futoshi; Fushiki, Ryosuke; Kubochi, Kei; Kimura, Fumiaki; Matsumura, Hideo

    2017-09-19

    The purpose of the present study was to evaluate the effect of priming agents and artificial aging with thermocycling on shear bond strengths of two resin-based luting agents to a translucent zirconia material. A total of 308 pairs of translucent zirconia disk specimens were divided into seven treatment groups: Alloy Primer (ALP), Clearfil Ceramic Primer Plus (CCP), Meta Fast Bonding Liner (MFB), MR. bond (MRB), Super-Bond PZ Primer Liquid B (PZB), V-Primer (VPR), and an unprimed group (UP). The specimens in each group were bonded with Panavia V5 Universal (UNI) and Opaque shade (OPA). Shear bond strengths (n=11 each) were tested before and after 5000 thermocycles. The data were analyzed with the Kruskal-Wallis test and the Steel-Dwass test. For both 0 and 5000 thermocycles, the ALP (47.8 and 41.5MPa, respectively) and CCP (45.8 and 42.3MPa, respectively) groups showed significantly higher bond strengths than other groups in the UNI luting agent. For the OPA luting agent, CCP group (45.8MPa) exhibited the highest pre-thermocycling bond strength in all groups. The ALP (32.4MPa) and CCP (36.5MPa) groups had significantly higher post-thermocycling shear bond strengths than other groups. In several groups, the shear bond strengths of the UNI luting agent were significantly higher than those of the OPA luting agent before and after thermocycling. Application of priming agents containing hydrophobic phosphate monomer (MDP) yielded the durable bond strengths of resin-based luting agents to a translucent zirconia material. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  13. Ab initio investigation of ground-states and ionic motion in particular in zirconia-based solid-oxide electrolytes

    International Nuclear Information System (INIS)

    Hirschfeld, Julian Arndt

    2012-01-01

    Electrolytes with high ionic conductivity at lower temperatures are the prerequisite for the success of Solid Oxide Fuel Cells (SOFC). One candidate is doped zirconia. In the past, the electrical resistance of zirconia based SOFC electrolytes has mainly been decreased by reducing its thickness. But there are limits to reducing the thickness and one can say that nowadays the normal ways are basically exhausted to further enhance the conductivity of well-known electrolyte materials. Hence, new approaches need to be found to discover windows of enhanced ionic conductivity. This can be achieved by understanding the quantum-mechanical oxygen transport in unconventional configurations of doped zirconia. Therefore, such an understanding is of fundamental importance. In this thesis two approaches are pursued, the investigation of the strain dependent ionic migration in zirconia based electrolytes and the designing of an electrolyte material structure with enhanced and strongly anisotropic ionic conductivity. The first approach expands the elementary understanding of oxygen migration in oxide lattices. The migration barrier of the oxygen ion jumps in zirconia is determined by applying the Density Functional Theory (DFT) calculations in connection with the Nudged Elastic Band (NEB) method. These computations show an unexpected window of decreased migration barriers at high compressive strains. Similar to other publications a decrease in the migration barrier for expansive strain is observed. But, in addition, a migration barrier decrease under high compressive strains is found beyond a maximal height of the migration barrier. A simple analytic model offers an explanation. The drop of the migration barrier at high compressions originates from the elevation of the ground-state energy. This means: Increasing ground state energies becomes an interesting alternative to facilitate ionic mobility. The second approach is based on the idea, that actually, only in the direction of ion

  14. Ab initio investigation of ground-states and ionic motion in particular in zirconia-based solid-oxide electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Hirschfeld, Julian Arndt

    2012-12-11

    Electrolytes with high ionic conductivity at lower temperatures are the prerequisite for the success of Solid Oxide Fuel Cells (SOFC). One candidate is doped zirconia. In the past, the electrical resistance of zirconia based SOFC electrolytes has mainly been decreased by reducing its thickness. But there are limits to reducing the thickness and one can say that nowadays the normal ways are basically exhausted to further enhance the conductivity of well-known electrolyte materials. Hence, new approaches need to be found to discover windows of enhanced ionic conductivity. This can be achieved by understanding the quantum-mechanical oxygen transport in unconventional configurations of doped zirconia. Therefore, such an understanding is of fundamental importance. In this thesis two approaches are pursued, the investigation of the strain dependent ionic migration in zirconia based electrolytes and the designing of an electrolyte material structure with enhanced and strongly anisotropic ionic conductivity. The first approach expands the elementary understanding of oxygen migration in oxide lattices. The migration barrier of the oxygen ion jumps in zirconia is determined by applying the Density Functional Theory (DFT) calculations in connection with the Nudged Elastic Band (NEB) method. These computations show an unexpected window of decreased migration barriers at high compressive strains. Similar to other publications a decrease in the migration barrier for expansive strain is observed. But, in addition, a migration barrier decrease under high compressive strains is found beyond a maximal height of the migration barrier. A simple analytic model offers an explanation. The drop of the migration barrier at high compressions originates from the elevation of the ground-state energy. This means: Increasing ground state energies becomes an interesting alternative to facilitate ionic mobility. The second approach is based on the idea, that actually, only in the direction of ion

  15. Synthesis and ceramic processing of alumina and zirconia based composites infiltrated with glass phase for dental applications

    International Nuclear Information System (INIS)

    Duarte, Daniel Gomes

    2009-01-01

    The interest for the use of ceramic materials for dental applications started due to the good aesthetic appearance promoted by the similarity to natural teeth. However, the fragility of traditional ceramics was a limitation for their use in stress conditions. The development of alumina and zirconia based materials, that associate aesthetic results, biocompatibility and good mechanical behaviour, makes possible the employment of ceramics for fabrication of dental restorations. The incorporation of vitreous phase in these ceramics is an alternative to minimize the ceramic retraction and to improve the adhesion to resin-based cements, necessary for the union of ceramic frameworks to the remaining dental structure. In the dentistry field, alumina and zirconia ceramic infiltrated with glassy phase are represented commercially by the In-Ceram systems. Considering that the improvement of powder's synthesis routes and of techniques of ceramic processing contributes for good performance of these materials, the goal of the present work is the study of processing conditions of alumina and/or 3 mol% yttria-stabilized zirconia ceramics infiltrated with aluminum borosilicate lanthanum glass. The powders, synthesized by hydroxide coprecipitation route, were pressed by uniaxial compaction and pre-sintered at temperature range between 950 and 1650 degree C in order to obtain porous ceramics bodies. Vitreous phase incorporation was performed by impregnation of aluminum borosilicate lanthanum powder, also prepared in this work, followed by heat treatment between 1200 and 1400 degree C .Ceramic powders were characterized by thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, gaseous adsorption (BET) and laser diffraction. Sinterability of alumina and /or stabilized zirconia green pellets was evaluated by dilatometry. Pre-sintered ceramics were characterized by apparent density measurements (Archimedes method), X-ray diffraction and scanning electron

  16. Stock Versus CAD/CAM Customized Zirconia Implant Abutments – Clinical and Patient‐Based Outcomes in a Randomized Controlled Clinical Trial

    Science.gov (United States)

    Meijer, Henny J.A.; Kerdijk, Wouter; Raghoebar, Gerry M.; Cune, Marco

    2016-01-01

    Abstract Background Single‐tooth replacement often requires a prefabricated dental implant and a customized crown. The benefits of individualization of the abutment remain unclear. Purpose This randomized controlled clinical trial aims to study potential benefits of individualization of zirconia implant abutments with respect to preservation of marginal bone level and several clinical and patient‐based outcome measures. Material and Methods Fifty participants with a missing premolar were included and randomly assigned to standard (ZirDesign, DentsplySirona Implants, Mölndal, Sweden) or computer aided design/computer aided manufacturing (CAD/CAM) customized (Atlantis, DentsplySirona Implants, Mölndal, Sweden) zirconia abutment therapy. Peri‐implant bone level (primary outcome), Plaque‐index, calculus formation, bleeding on probing, gingiva index, probing pocket depth, recession, appearance of soft tissues and patients' contentment were assessed shortly after placement and one year later. Results No implants were lost and no complications related to the abutments were observed. Statistically significant differences between stock and CAD/CAM customized zirconia abutments could not be demonstrated for any of the operationalized variables. Conclusion The use of a CAD/CAM customized zirconia abutment in single tooth replacement of a premolar is not associated with an improvement in clinical performance or patients' contentment when compared to the use of a stock zirconia abutment. PMID:27476829

  17. Stock Versus CAD/CAM Customized Zirconia Implant Abutments - Clinical and Patient-Based Outcomes in a Randomized Controlled Clinical Trial.

    Science.gov (United States)

    Schepke, Ulf; Meijer, Henny J A; Kerdijk, Wouter; Raghoebar, Gerry M; Cune, Marco

    2017-02-01

    Single-tooth replacement often requires a prefabricated dental implant and a customized crown. The benefits of individualization of the abutment remain unclear. This randomized controlled clinical trial aims to study potential benefits of individualization of zirconia implant abutments with respect to preservation of marginal bone level and several clinical and patient-based outcome measures. Fifty participants with a missing premolar were included and randomly assigned to standard (ZirDesign, DentsplySirona Implants, Mölndal, Sweden) or computer aided design/computer aided manufacturing (CAD/CAM) customized (Atlantis, DentsplySirona Implants, Mölndal, Sweden) zirconia abutment therapy. Peri-implant bone level (primary outcome), Plaque-index, calculus formation, bleeding on probing, gingiva index, probing pocket depth, recession, appearance of soft tissues and patients' contentment were assessed shortly after placement and one year later. No implants were lost and no complications related to the abutments were observed. Statistically significant differences between stock and CAD/CAM customized zirconia abutments could not be demonstrated for any of the operationalized variables. The use of a CAD/CAM customized zirconia abutment in single tooth replacement of a premolar is not associated with an improvement in clinical performance or patients' contentment when compared to the use of a stock zirconia abutment. © 2016 The Authors. Clinical Implant Dentistry and Related Research Published by Wiley Periodicals, Inc.

  18. Electrocatalytic oxidation of ethanol in acid medium: Enhancement of activity of vulcan-supported Platinum-based nanoparticles upon immobilization within nanostructured zirconia matrices

    Science.gov (United States)

    Rutkowska, Iwona A.; Kulesza, Pawel J.

    2014-09-01

    Composite electrocatalytic materials that utilize carbon (Vulcan) supported Pt or PtRu nanoparticles dispersed within thin films of zirconia (ZrO2) are considered here for oxidation of such a biofuel as ethanol in acid medium. The systems were characterized using electrochemical techniques as well as transmission electron microscopy. The enhancement of activity was clearly evident upon comparison of the respective voltammetric and chronoamperometric current densities recorded (at room temperature in 0.5 mol dm-3H2SO4 containing 0.5 mol dm-3 ethanol) using the Vulcan supported Pt and PtRu catalysts in the presence and absence of zirconia. In all cases, the noble metal loading was the same, 100 μg cm-2. Apparently, the existence of large population of hydroxyl groups (originating from zirconia) in the vicinity of Pt-based catalyst, in addition to possible specific interactions between zirconia and the ruthenium component of PtRu, facilitated the oxidative removal (from Pt) of the passivating (e.g., CO) reaction intermediates (adsorbates). By utilizing carbon supported, rather than bare or unsupported, Pt or PtRu nanoparticles (dispersed within the semiconducting zirconia), the overall charge distribution at the electrocatalytic interface was improved.

  19. Large scale synthesis of nanostructured zirconia-based compounds from freeze-dried precursors

    Science.gov (United States)

    Gómez, A.; Villanueva, R.; Vie, D.; Murcia-Mascaros, S.; Martínez, E.; Beltrán, A.; Sapiña, F.; Vicent, M.; Sánchez, E.

    2013-01-01

    Nanocrystalline zirconia powders have been obtained at the multigram scale by thermal decomposition of precursors resulting from the freeze-drying of aqueous acetic solutions. This technique has equally made possible to synthesize a variety of nanostructured yttria or scandia doped zirconia compositions. SEM images, as well as the analysis of the XRD patterns, show the nanoparticulated character of those solids obtained at low temperature, with typical particle size in the 10-15 nm range when prepared at 673 K. The presence of the monoclinic, the tetragonal or both phases depends on the temperature of the thermal treatment, the doping concentration and the nature of the dopant. In addition, Rietveld refinement of the XRD profiles of selected samples allows detecting the coexistence of the tetragonal and the cubic phases for high doping concentration and high thermal treatment temperatures. Raman experiments suggest the presence of both phases also at relatively low treatment temperatures.

  20. Effect of screw access hole preparation on fracture load of implant-supported zirconia-based crowns: an in vitro study

    Directory of Open Access Journals (Sweden)

    Hadi Mokhtarpour

    2016-07-01

    Full Text Available Background. Fracture load of implant-supported restorations is an important factor in clinical success. This study evaluated the effect of two techniques for screw access hole preparation on the fracture load of cement-screw-retained implant-supported zirconia-based crowns. Methods. Thirty similar cement-screw-retained implant-supported zirconia-based maxillary central incisor crowns were evaluated in three groups of 10. Group NH: with no screw access holes for the control; Group HBS: with screw access holes prepared with a machine before zirconia sintering; Group HAS: with screw access holes prepared manually after zirconia sintering. In group HBS, the access holes were virtually designed and prepared by a computer-assisted design/computer-assisted manufacturing system. In group HAS, the access holes were manually prepared after zirconia sintering using a diamond bur. The dimensions of the screw access holes were equal in both groups. The crowns were cemented onto same-size abutments and were then subjected to thermocycling. The fracture load values of the crowns were measured using a universal testing machine. Data were analyzed with ANOVA and Tukey test (P < 0.05. Results. The mean fracture load value for the group NH was 888.37 ± 228.92 N, which was the highest among the groups, with a significant difference (P < 0.0001. The fracture load values were 610.48 ± 125.02 N and 496.74 ± 104.10 Nin the HBS and HAS groups, respectively, with no significant differences (P = 0.44. Conclusion. Both techniques used for preparation of screw access holes in implant-supported zirconia-based crowns de-creased the fracture load.

  1. Clinical trials in zirconia: a systematic review.

    Science.gov (United States)

    Al-Amleh, B; Lyons, K; Swain, M

    2010-08-01

    Zirconia is unique in its polymorphic crystalline makeup, reported to be sensitive to manufacturing and handling processes, and there is debate about which processing method is least harmful to the final product. Currently, zirconia restorations are manufactured by either soft or hard-milling processes, with the manufacturer of each claiming advantages over the other. Chipping of the veneering porcelain is reported as a common problem and has been labelled as its main clinical setback. The objective of this systematic review is to report on the clinical success of zirconia-based restorations fabricated by both milling processes, in regard to framework fractures and veneering porcelain chipping. A comprehensive review of the literature was completed for in vivo trials on zirconia restorations in MEDLINE and PubMed between 1950 and 2009. A manual hand search of relevant dental journals was also completed. Seventeen clinical trials involving zirconia-based restorations were found, 13 were conducted on fixed partial dentures, two on single crowns and two on zirconia implant abutments, of which 11 were based on soft-milled zirconia and six on hard-milled zirconia. Chipping of the veneering porcelain was a common occurrence, and framework fracture was only observed in soft-milled zirconia. Based on the limited number of short-term in vivo studies, zirconia appears to be suitable for the fabrication of single crowns, and fixed partial dentures and implant abutments providing strict protocols during the manufacturing and delivery process are adhered to. Further long-term prospective studies are necessary to establish the best manufacturing process for zirconia-based restorations.

  2. Structural reliability of alumina-, feldspar-, leucite-, mica- and zirconia-based ceramics.

    Science.gov (United States)

    Tinschert, J; Zwez, D; Marx, R; Anusavice, K J

    2000-09-01

    The objective of this study was to test the hypothesis that industrially manufactured ceramic materials, such as Cerec Mark II and Zirconia-TZP, have a smaller range of fracture strength variation and therefore greater structural reliability than laboratory-processed dental ceramic materials. Thirty bar specimens per material were prepared and tested. The four-point bend test was used to determine the flexure strength of all ceramic materials. The fracture stress values were analyzed by Weibull analysis to determine the Weibull modulus values (m) and the 1 and 5% probabilities of failure. The mean strength and standard deviation values for these ceramics are as follows: (MPa+/-SD) were: Cerec Mark II, 86.3+/-4.3; Dicor, 70.3+/-12.2; In-Ceram Alumina, 429. 3+/-87.2; IPS Empress, 83.9+/-11.3; Vitadur Alpha Core, 131.0+/-9.5; Vitadur Alpha Dentin, 60.7+/-6.8; Vita VMK 68, 82.7+/-10.0; and Zirconia-TZP, 913.0+/-50.2. There was no statistically significant difference among the flexure strength of Cerec Mark II, Dicor, IPS Empress, Vitadur Alpha Dentin, and Vita VMK 68 ceramics (p>0.05). The highest Weibull moduli were associated with Cerec Mark II and Zirconia-TZP ceramics (23.6 and 18.4). Dicor glass-ceramic and In-Ceram Alumina had the lowest m values (5.5 and 5.7), whereas intermediate values were observed for IPS-Empress, Vita VMK 68, Vitadur Alpha Dentin and Vitadur Alpha Core ceramics (8.6, 8.9, 10.0 and 13.0, respectively). Except for In-Ceram Alumina, Vitadur Alpha and Zirconia-TZP core ceramics, most of the investigated ceramic materials fabricated under the condition of a dental laboratory were not stronger or more structurally reliable than Vita VMK 68 veneering porcelain. Only Cerec Mark II and Zirconia-TZP specimens, which were prepared from an industrially optimized ceramic material, exhibited m values greater than 18. Hence, we conclude that industrially prepared ceramics are more structurally reliable materials for dental applications although CAD

  3. A reversible adsorption-desorption interface of DNA based on nano-sized zirconia and its application.

    Science.gov (United States)

    Liu, Shou-Qing; Xu, Jing-Juan; Chen, Hong-Yuan

    2004-08-01

    It is essential for the information storage in DNA-based bio-chips to construct a reversible exchange interface of DNA. Here, a highly reproducible and reversible adsorption-desorption interface of DNA based on the nano-sized zirconia in different pH solution was successfully fabricated. The results showed that DNA can be adsorbed onto the nano-sized zirconia from its solution, and can desorb from the nanoparticles in 0.10 M KOH solution. When the matrix with nanoparticles returns to the DNA solution again, DNA can be re-adsorbed onto them as initial state. Moreover, the interaction of DNA with non-electroactive molecules, 2,2'-bipyridine, has been studied by electrochemistry method in the aid of probe Co(phen)(3)(3+). The experiments showed that when 2,2'-bipyridine was added into the test solution, the voltammetric peak currents of Co(phen)(3)(3+) decreased; and the decrease value of peak current against the concentration of 2,2'-bipyridine has a good Langmuir relationship, by which the equilibrium constant of interaction between 2,2'-bipyridine and DNA was estimated to be 1.57 x 10(4)M(-1).

  4. Partial-retainer design considerations for zirconia restorations

    NARCIS (Netherlands)

    Aboushelib, M.N.; Feilzer, A.J.; Kleverlaan, C.J.; Salameh, Z.

    2010-01-01

    Objective: Bond strength limitations of adhesive zirconia restorations have stood as a barrier against their widespread use. Selective infiltration etching is a new surface treatment that enhances bonding to zirconia-based materials. Beside bond strength, the performance of adhesive zirconia

  5. Effect of an experimental zirconia-silica coating technique on micro tensile bond strength of zirconia in different priming conditions

    NARCIS (Netherlands)

    Chen, C.; Kleverlaan, C.J.; Feilzer, A.J.

    2012-01-01

    Objectives This study aimed to evaluate the adhesive properties of a MDP-containing resin cement to a colored zirconia ceramic, using an experimental zirconia-silica coating technique with different priming conditions. Methods 18 zirconia ceramic discs (Cercon base colored) were divided into two

  6. Hot Corrosion of Yttrium Stabilized Zirconia Coatings Deposited by Air Plasma Spray on a Nickel-Based Superalloy

    Science.gov (United States)

    Vallejo, N. Diaz; Sanchez, O.; Caicedo, J. C.; Aperador, W.; Zambrano, G.

    In this research, the electrochemical impedance spectroscopy (EIS) and Tafel analysis were utilized to study the hot corrosion performance at 700∘C of air plasma-sprayed (APS) yttria-stabilized zirconia (YSZ) coatings with a NiCrAlY bond coat grown by high velocity oxygen fuel spraying (HVOF), deposited on an INCONEL 625 substrate, in contact with corrosive solids salts as vanadium pentoxide V2O5 and sodium sulfate Na2SO4. The EIS data were interpreted based on proposed equivalent electrical circuits using a suitable fitting procedure performed with Echem AnalystTM Software. Phase transformations and microstructural development were examined using X-ray diffraction (XRD), with Rietveld refinement for quantitative phase analysis, scanning electron microscopy (SEM) was used to determinate the coating morphology and corrosion products. The XRD analysis indicated that the reaction between sodium vanadate (NaVO3) and yttrium oxide (Y2O3) produces yttrium vanadate (YVO4) and leads to the transformation from tetragonal to monoclinic zirconia phase.

  7. Evaluation of a new carbon/zirconia-based sorbent for the cleanup of food extracts in multiclass analysis of pesticides and environmental contaminants

    Science.gov (United States)

    A novel carbon/zirconia based material, SupelTM QuE Verde (Verde), was evaluated in a filter-vial dispersive solid phase extraction (d-SPE) cleanup of QuEChERS extracts of pork, salmon, kale, and avocado for residual analysis of pesticides and environmental contaminants. Low pressure (LP) GC-MS/MS w...

  8. Fracture resistance of zirconia-composite veneered crowns in comparison with zirconia-porcelain crowns.

    OpenAIRE

    Alsadon, O.; Patrick, D.; Johnson, A.; Pollington, S.; Wood, D.

    2017-01-01

    The objectives were to evaluate the fracture resistance and stress concentration in zirconia/composite veneered crowns in comparison to zirconia/porcelain crowns using occlusal fracture resistance and by stress analysis using finite element analysis method. Zirconia substructures were divided into two groups based on the veneering material. A static load was applied occlusally using a ball indenter and the load to fracture was recorded in Newtons (N). The same crown design was used to create ...

  9. THE EFFECT OFCARBON NANOTUBES ON THE SINTERING BEHAVIOR OF ZIRCONIA BASED MATERIALS

    OpenAIRE

    A. M. Zahedi; H. R. Rezaie; J. Javadpour

    2015-01-01

    Different volume fractions (1.3, 2.6, and 7.6 Vol.%) of carbon nanotubes (CNTs) were dispersed within 8Y-TZP nanopowders. Mixed powder specimens were subsequently processed by spark plasma sintering (SPS) and effects of CNTs on the sintering process of 8Y-TZP/CNT composites was studied. Maintenance of CNTs through the SPS process was confirmed using TEM and Raman Spectroscopy. Studies on the sintering profile of zirconia-CNT composites (Z-xC composites) could, to some extent, clarify the effe...

  10. Crack growth resistance of alumina, zirconia and zirconia toughened alumina ceramics for joint prostheses.

    Science.gov (United States)

    De Aza, A H; Chevalier, J; Fantozzi, G; Schehl, M; Torrecillas, R

    2002-02-01

    Mono-phase bio-ceramics (alumina and zirconia) are widely used as femoral heads in total hip replacements (THR) as an alternative to metal devices. Unfortunately, the orthopaedic community reports significant in-vivo failures. Material scientists are already familiar with composites like alumina zirconia. Since both are biocompatible, this could prove to be a new approach to implants. This paper deals with a new generation of alumina-zirconia nano-composites having a high resistance to crack propagation, and as a consequence may offer the option to improve lifetime and reliability of ceramic joint prostheses. The reliability of the above mentioned three bio-ceramics (alumina, zirconia and zirconia toughened alumina) for THR components is analysed based on the study of their slow crack-growth behaviour. The influence of the processing conditions on the microstructure development, of the zirconia toughened alumina composites and the effect of these microstructures, on its mechanical properties, are discussed.

  11. Zirconia based superhydrophobic coatings on cotton fabrics exhibiting excellent durability for versatile use

    Science.gov (United States)

    Das, Indranee; De, Goutam

    2015-01-01

    A fluorinated silyl functionalized zirconia was synthesized by the sol-gel method to fabricate an extremely durable superhydrophobic coating on cotton fabrics by simple immersion technique. The fabric surfaces firmly attached with the coating material through covalent bonding, possessed superhydrophobicity with high water contact angle ≈163 ± 1°, low hysteresis ≈3.5° and superoleophilicity. The coated fabrics were effective to separate oil/water mixture with a considerably high separation efficiency of 98.8 wt% through ordinary filtering. Presence of highly stable (chemically and mechanically) superhydrophobic zirconia bonded with cellulose makes such excellent water repelling ability of the fabrics durable under harsh environment conditions like high temperature, strong acidic or alkaline solutions, different organic solvents and mechanical forces including extensive washings. Moreover, these coated fabrics retained self-cleanable superhydrophobic property as well as high water separation efficiency even after several cycles, launderings and abrasions. Therefore, such robust superhydrophobic ZrO2 coated fabrics have strong potential for various industrial productions and uses. PMID:26678754

  12. Influence of surface pretreatment on the short-term bond strength of resin composite to a zirconia-based material.

    Science.gov (United States)

    Fazi, Giovanni; Vichi, Alessandro; Ferrari, Marco

    2012-04-01

    To evaluate the influence of airborne-particle abrasion of zirconia before and after sintering, on the bond strength between a zirconia core and an indirect resin composite material. 9 disks of Y-TZP zirconia core were prepared and divided into three equal groups. In Group 1 pre-sintered Y-TZP zirconia was airborne-particle abraded with 120 microm alumina oxide. In Group 2 sintered Y-TZP zirconia was airborne-particle abraded with 120 microm alumina oxide. In Group 3 sintered Y-TZP zirconia was not treated and thus served as the control group. A 10-methacryloylooxydecyldihydrogenphosphate (MDP) containing bonding agent and silane coupling agent mixture was applied to the disks in all three experimental groups. Resin composite for indirect restorations was incrementally layered in a plastic mold to a final thickness of 3 mm. Specimens were sectioned under water cooling to obtain microsticks 6 x 1 x 1 mm in dimension. 30 microsticks per experimental group were generated. Microtensile bond strength test was conducted with a universal testing machine. Fractured microsticks and sections from each group were also examined under an optical microscope and a scanning electron microscope to evaluate respectively the mode of failure and the zirconia-composite interface. T-test for independent samples was selected to analyze the data. The level of significance was set at P resin composite bond. Airborne-particle abrasion performed before sintering zirconia did not produce any significant differences.

  13. Influence of surface treatment on the in-vitro fracture resistance of zirconia-based all-ceramic anterior crowns.

    Science.gov (United States)

    Schmitter, M; Lotze, G; Bömicke, W; Rues, S

    2015-12-01

    The purpose of this study was to assess the effect of surface treatment on the fracture resistance of zirconia-based all-ceramic anterior crowns. Sixty-four zirconia-based all-ceramic anterior crowns, veneered by use of a press-on technique, were produced. For 48 crowns intraoral adjustment was simulated (A-group), 16 crowns remained unadjusted (WA-group). The adjusted area was then treated in three ways: 1. no further surface treatment; 2. polishing, with irrigation, using polishers interspersed with diamond grit for ceramics; and 3. polishing and glaze firing. Half of the specimens were loaded until fracture in an universal testing device without artificial ageing; the other crowns underwent thermocycling and chewing simulation before ultimate-load testing. Explorative statistical analysis was performed by use of non-parametric and parametric tests. In addition, fracture-strength tests according to ISO 6872 were performed for veneer ceramic subjected to the different surface treatments. Finite element analysis was also conducted for the crowns, and surface roughness was measured. Crowns in the A-group were more sensitive to aging than crowns in the WA-group (p=0.038). Although both polishing and glaze firing slightly improved the fracture resistance of the specimens, the fracture resistance in the WA-group (initial fracture resistance (IFR): 652.0 ± 107.7N, remaining fracture resistance after aging (RFR): 560.6 ± 233.3N) was higher than the fracture resistance in the A-group (polished: IFR: 477.9 ± 108.8N, RFR: 386.0 ± 218.5N; glaze firing: IFR: 535.5 ± 128.0N, RFR: 388.6 ± 202.2N). Surface roughness without adjustment was Ra=0.1 μm; for adjustment but without further treatment it was Ra=1.4 μm; for adjustment and polishing it was Ra=0.3 μm; and for adjustment, polishing, and glazing it was Ra=0.6 μm. Stress distributions obtained by finite element analysis in combination with fracture strength tests showed that fractures most probably originated from

  14. Analysis of the peri-implant soft tissues in contact with zirconia abutments: an evidence-based literature review.

    Science.gov (United States)

    de Medeiros, Rodrigo Antonio; Vechiato-Filho, Aljomar José; Pellizzer, Eduardo Piza; Mazaro, Jose Vitor Quinelli; dos Santos, Daniela Micheline; Goiato, Marcelo Coelho

    2013-05-01

    The aim of this study is to evaluate through a literature review, the soft tissue response in contact with zirconia abutments, including case reports comparing prosthetics rehabilitations with zirconia and titanium abutments upto 3 years of follow-up as well as the factors that should be considered on implant's abutment selection. Metallic abutments can provide grayish color when in contact with thin soft tissues which may lead the implant prosthetic treatment to failure. In this context, the abutments of zirconia stand out because there is an excellent linking between esthetics and the health of peri-implant soft tissues. A consult of the published researches was made on the PubMed database from 2000 to September 2012. The including criteria were: literature reviews, clinical studies and case reports in English that focused on the response of the soft tissue in contact with zirconia implant abutments. The studies that were not in English and did not match the tackled issue were excluded. A total of 32 articles were found. According to the search strategy, just 16 articles were selected for this review. Three studies affirmed that zirconia abutments have an excellent soft tissue response; one study showed increased gingival recession with zirconia abutments and nine studies do not stand out any difference on biological behavior between titanium and zirconia abutments. Three studies affirmed that zirconia abutments provide natural gingival appearance, anatomic contour and greater esthetics. The use of zirconia abutments is recommended for anterior regions because of their greater optical properties and esthetic results and more studies should be performed and analyzed longitudinally regarding their biological response. The zirconia abutments have been established to be essential in order to achieve great esthetic results in cases of thin peri-implant soft tissues and in regions where the three-dimensional placement of implants is more superficial.

  15. Clinical evaluation of 1,132 zirconia-based single crowns: a retrospective cohort study from the AIOP clinical research group.

    Science.gov (United States)

    Monaco, Carlo; Caldari, Mauro; Scotti, Roberto

    2013-01-01

    The aim of this retrospective cohort study was to gather the outcomes of zirconia single crowns made by 16 members of the Italian Academy of Prosthetic Dentistry (AIOP) over a time period of up to 5 years. A total of 398 patients treated in private practices with 1,132 zirconia-based single-crown restorations made on natural teeth from January 2005 to July 2010 were included. Three hundred forty-three anterior restorations (30.3%) and 789 posterior crowns (69.7%) were made with 16 types of zirconia, using primarily chamfer or knife-edge tooth preparation, and examined according to the esthetic, functional, and biologic criteria. To evaluate the relationship of parafunction with mechanical failure, patients with clenching or bruxism were not excluded from the study group. The cumulative survival rate of all restorations was 98.1%, while the cumulative success rate was 94.3%. Functional criteria had the highest number of failures. The odds ratio (OR) for all restorations was calculated to clarify the relationship between patients who were subject/not subject to parafunctions and technical complications; the OR was 2.60. An association between parafunction and mechanical failure was found in patients with severe parafunction. Porcelain-veneered zirconia single crowns with chamfer and knife-edge preparations showed good clinical results over a period of up to 5 years. Technical complications were few and were limited primarily to patients with parafunction.

  16. Comparison of implant versus tooth-supported zirconia-based single crowns in a split-mouth design: a 4-year clinical follow-up study.

    Science.gov (United States)

    Güncü, Mustafa Barış; Cakan, Umut; Aktas, Guliz; Güncü, Güliz Nigar; Canay, Şenay

    2016-12-01

    This study aims to evaluate the 4-year clinical performance of tooth versus implant-supported single-unit zirconia crowns (LAVA™) placed on posterior region. Twenty-four patients (10 men and 14 women) who had received 48 single crowns (24 implant-supported and 24 tooth-supported) from January 2007 to December 2009, were included. California Dental Association (CDA) quality assessment system, plaque and gingival index scores were used to evaluate the performance of the crowns at baseline and at all follow-up examinations. During the follow-up period, no fracture of zirconia coping has occurred. Major complication was chipping in three patients that required a new crown fabrication. Except for the failure ones, all crowns in both groups were rated as satisfactory at the follow-up examinations based on the CDA quality assessment criteria. There were no statistically significant differences between tooth and implant-supported crowns in terms of periodontal parameters. The present 4-year follow-up clinical study demonstrates that single-unit tooth- and implant-supported zirconia crowns have similar prosthetic and periodontal outcomes. Single-unit implant or tooth-supported zirconia crowns may be considered acceptable treatment modalities for restoration of either missing or compromised posterior teeth.

  17. Characterization and optimization of a chromatographic process based on ethylenediamine-N,N,N',N'-tetra(methylphosphonic) acid-modified zirconia particles.

    Science.gov (United States)

    Sarkar, Sabyasachi; Carr, Peter W; McNeff, Clayton V; Subramanian, Anu

    2003-06-25

    The primary objective of work was to characterize, optimize and model a chromatographic process based on ethylenediamine-N,N,N',N'-tetra(methylphosphonic) acid (EDTPA)-modified zirconia particles. Zirconia particles were produced by spray-drying colloidal zirconia. Zirconia spheres produced were further classified, calcined and modified with EDTPA to yield a solid-phase support for use in bio-chromatography (r_PEZ). Specifically, the ability of r_PEZ to selectively bind and enrich IgG, IgA, and IgM from biological fluids was evaluated and demonstrated. To better understand the force of interaction between the IgG and the r_PEZ, the equilibrium disassociation constant (K(d)) was determined by static binding isotherms, as a function of temperature and by frontal analysis at different linear velocities. The maximum static binding capacity (Q(max)) was found to be in the range 55-65 mg IgG per ml of beads, and unaffected by temperature. The maximum dynamic binding capacity (Q(x)) was found to be in the range 20-12 mg IgG per ml of beads. The adsorption rate constant (k(a)) was determined by a split-peak approach to be between 982 and 3242 l mol(-1) s(-1) depending on the linear velocity. The standard enthalpy and entropy values were estimated for this interaction of IgG with this novel support.

  18. Brazing of Stainless Steel to Yttria-Stabilized Zirconia Using Gold-Based Brazes for Solid Oxide Fuel Cell Applications

    Science.gov (United States)

    Singh, M.; Shpargel, T. P.; Asthana, R.

    2007-01-01

    Two gold-base active metal brazes (gold-ABA and gold-ABA-V) were evaluated for oxidation resistance to 850 C, and used to join yttria-stabilized zirconia (YSZ) to a corrosion-resistant ferritic stainless steel for possible use in solid oxide fuel cells. Thermogravimetric analysis and optical microscopy and scanning electron microscopy coupled with energy-dispersive spectroscopy were used to evaluate the braze oxidation behavior, and microstructure and composition of the YSZ/braze/steel joints. Both gold-ABA and gold-ABA-V exhibited nearly linear oxidation kinetics at 850 C, with gold-ABA-V showing faster oxidation than gold-ABA. Both brazes produced metallurgically sound YSZ/steel joints due to chemical interactions of Ti and V with the YSZ and steel substrates.

  19. The wetting characteristics and surface tension of some Ni-based alloys on yttria, hafnia, alumina, and zirconia substrates

    Science.gov (United States)

    Kanetkar, C. S.; Kacar, A. S.; Stefanescu, D. M.

    1988-01-01

    The surface tension and wetting characteristics of four commercial Ni-based alloys (UD718, Waspaloy, UD720, and UD520), pure Ni, and three special alloys (Ni-20 percent Cr, Ni-20 percent Cr-1 percent Al, and Ni-20 percent Cr-4 percent Al) on various ceramic substrates (including alumina, zirconia, hafnia, and yttria) were investigated using sessile drop experiments. Most of the systems studied exhibited a nonwetting behavior. Wetting improved with holding time at a given temperature to the point that some systems, such as Ni-20Cr on alumina, Ni-20Cr-4Al on alumina and on yttria, became marginally wetting. Wetting characteristics were apparently related to constitutional undercooling, which in turn could be affected by the metal dissolving some of the substrate during measurements.

  20. Practice-based clinical evaluation of zirconia abutments for anterior single-tooth restorations.

    Science.gov (United States)

    Rinke, Sven; Lattke, Anja; Eickholz, Peter; Kramer, Katharina; Ziebolz, Dirk

    2015-01-01

    This study aimed to determine the survival rate and prevalence of biologic and technical complications associated with single-tooth implants with all-ceramic abutments in the anterior region. A total of 33 patients were restored with 50 anterior implants and temporarily luted all-ceramic crowns on prefabricated zirconia abutments. All of the patients subsequently received annual supportive maintenance; 27 patients (18 women, 22-74 years) with 42 implants participated in the final maintenance visit and were included in the study (follow-up 78.1 ± 27.0 months). The time-dependent survival rate (Kaplan-Meier) and the frequency of prosthetic complications (abutment fracture [AF], screw loosening [SL], fracture of veneering ceramics [VF], retention loss [RL]) and biologic complications (peri-implantitis) were calculated to determine the success rates. No implant loss (implant-related survival rate 100%) but one abutment fracture occurred throughout the entire observation period; therefore, the survival rate of the superstructures (in situ criterion) was 97.6% (95% confidence interval [CI] 0.930- 1.000) after 7 years. Eleven restorations were affected by prosthetic complications: RL (n = 4), VF (n = 5), and SL (n = 2). Peri-implantitis was diagnosed for two implants (probing depth > 5 mm, bleeding on probing [BOP]/suppuration, and bone loss > 3 mm) (implant-related peri-implantitis rate 4.8%). No restoration required replacement due to complications. The success rate (event-free restoration) was 75.9% (95% CI 0.636- 0.882) after 7 years. Considering the calculated survival rate, the application of all-ceramic zirconia implant abutments in the anterior region can be recommended as a reliable therapy in private practice. Fractures of veneering ceramics were the most common prosthetic complication.

  1. Marginal and internal fit of zirconia based fixed dental prostheses fabricated with different concepts

    Directory of Open Access Journals (Sweden)

    Florian Beuer

    2010-02-01

    Full Text Available Florian Beuer1, Natalie Korczynski1, Antonia Rezac1, Michael Naumann2, Wolfgang Gernet1, John A Sorensen31Department of Prosthodontics, Ludwig-Maximilians University, Munich, Germany; 2Department of Prosthodontics and Material Sciences, University of Ulm, Germany; 3Pacific Dental Institute, Portland, Oregon, USAAbstract: The purpose of this in vitro study was to compare the precision of fit of substructures milled from semi-sintered zirconia blocks, fabricated with two different fabrication concepts. Three-unit, posterior fixed dental prostheses (FDP were fabricated for standardized dies (n = 10 with the laboratory Computer Aided Design (CAD/Computer Aided Manufacturing (CAM system Cercon® Brain (Brain and the centralized CAD/CAM system Compartis Integrated Systems (Compartis. After cementation to the dies, the FDP were embedded and sectioned. Four cross-sections were made of each abutment tooth, and marginal and internal fit were evaluated under an optical microscope. A one-way analysis of variance (ANOVA was used to compare data (α = 0.05. Mean gap dimensions at the marginal opening for Brain and Compartis were 56.0 (±34.5 μm and 51.7 (±45.2 μm, respectively. Mean internal gap dimensions of 62.8 (±37.5 μm to 164.6 (±33.4 μm were measured depending on the measurement location and the fabrication concept. Mean marginal openings and internal adaptations were not significantly different for both systems. Three out of four measurement locations showed significantly different cement gaps. Within the limitations of this study, the results suggest that the accuracy of both investigated systems is satisfactory for clinical use. The laboratory fabrication exhibited similar accuracy as the centralized manufacturing.Keywords: zirconia, CAD/CAM, fit, FDP, all-ceramic

  2. Large scale synthesis of nanostructured zirconia-based compounds from freeze-dried precursors

    International Nuclear Information System (INIS)

    Gómez, A.; Villanueva, R.; Vie, D.; Murcia-Mascaros, S.; Martínez, E.; Beltrán, A.; Sapiña, F.; Vicent, M.; Sánchez, E.

    2013-01-01

    Nanocrystalline zirconia powders have been obtained at the multigram scale by thermal decomposition of precursors resulting from the freeze-drying of aqueous acetic solutions. This technique has equally made possible to synthesize a variety of nanostructured yttria or scandia doped zirconia compositions. SEM images, as well as the analysis of the XRD patterns, show the nanoparticulated character of those solids obtained at low temperature, with typical particle size in the 10–15 nm range when prepared at 673 K. The presence of the monoclinic, the tetragonal or both phases depends on the temperature of the thermal treatment, the doping concentration and the nature of the dopant. In addition, Rietveld refinement of the XRD profiles of selected samples allows detecting the coexistence of the tetragonal and the cubic phases for high doping concentration and high thermal treatment temperatures. Raman experiments suggest the presence of both phases also at relatively low treatment temperatures. - Graphical abstract: Zr 1−x A x O 2−x/2 (A=Y, Sc; 0≤x≤0.12) solid solutions have been prepared as nanostructured powders by thermal decomposition of precursors obtained by freeze-drying, and this synthetic procedure has been scaled up to the 100 g scale. Highlights: ► Zr 1−x A x O 2−x/2 (A=Y, Sc; 0≤x≤0.12) solid solutions have been prepared as nanostructured powders. ► The synthetic method involves the thermal decomposition of precursors obtained by freeze-drying. ► The temperature of the thermal treatment controls particle sizes. ► The preparation procedure has been scaled up to the 100 g scale. ► This method is appropriate for the large-scale industrial preparation of multimetallic systems.

  3. Aqueous solubility of zirconia

    International Nuclear Information System (INIS)

    Sunder, S.; Wren, S.

    2008-01-01

    Zirconia (zirconium dioxide) is being considered as a host matrix for the disposal of actinides in a geologic disposal vault, for the 'burning of actinides' in nuclear reactors and for the use of lanthanides as burnable-neutron absorbers to control the neutron flux in the reactors. These applications require knowledge of the stability of the zirconia in aqueous environment. Therefore, a literature review of the aqueous solubility of zirconia was carried out. The literature review was complemented by experiments on the dissolution of zirconia in aqueous solutions. The paper presents the results of the literature review and our experiments on the dissolution of zirconia in solutions of pH between 5.7 and 10.3. The low solubility of zirconia in the solutions investigated here supports the selection of zirconia for the above applications. (author)

  4. Zirconia- versus metal-based, implant-supported abutments and crowns:Comparative studies on fracture mode and short-time clinical outcome

    OpenAIRE

    Hosseini, Mandana

    2012-01-01

    To restore oral functions in patients with missing teeth, single-tooth implants are a well-documented treatment option. Along with high survival rates, aesthetic factors have become an important clinical outcome variable for evaluating treatment success of implant-supported restorations. Thus, the selection of restoration materials should be based on proper optical characteristics in addition to biocompatibility and sufficient strength of materials. Abutments and crowns based on zirconia are ...

  5. On the interfacial fracture resistance of resin-bonded zirconia and glass-infiltrated graded zirconia

    Science.gov (United States)

    Chai, Herzl; Kaizer, Marina; Chughtai, Asima; Tong, Hui; Tanaka, Carina; Zhang, Yu

    2015-01-01

    Objective A major limiting factor for the widespread use of zirconia in prosthetic dentistry is its poor resin-cement bonding capabilities. We show that this deficiency can be overcome by infiltrating the zirconia cementation surface with glass. Current methods for assessing the fracture resistance of resin-ceramic bonds are marred by uneven stress distribution at the interface, which may result in erroneous interfacial fracture resistance values. We have applied a wedge-loaded double-cantilever-beam testing approach to accurately measure the interfacial fracture resistance of adhesively bonded zirconia-based restorative materials. Methods The interfacial fracture energy GC was determined for adhesively bonded zirconia, graded zirconia and feldspathic ceramic bars. The bonding surfaces were subjected to sandblasting or acid etching treatments. Baseline GC was measured for bonded specimens subjected to 7 days hydration at 37 °C. Long-term GC was determined for specimens exposed to 20,000 thermal cycles between 5 and 55 °C followed by 2-month aging at 37 °C in water. The test data were interpreted with the aid of a 2D finite element fracture analysis. Results The baseline and long-term GC for graded zirconia was 2–3 and 8 times that for zirconia, respectively. More significantly, both the baseline and long-term GC of graded zirconia were similar to those for feldspathic ceramic. Significance The interfacial fracture energy of feldspathic ceramic and graded zirconia was controlled by the fracture energy of the resin cement while that of zirconia by the interface. GC for the graded zirconia was as large as for feldspathic ceramic, making it an attractive material for use in dentistry. PMID:26365987

  6. On the interfacial fracture resistance of resin-bonded zirconia and glass-infiltrated graded zirconia.

    Science.gov (United States)

    Chai, Herzl; Kaizer, Marina; Chughtai, Asima; Tong, Hui; Tanaka, Carina; Zhang, Yu

    2015-11-01

    A major limiting factor for the widespread use of zirconia in prosthetic dentistry is its poor resin-cement bonding capabilities. We show that this deficiency can be overcome by infiltrating the zirconia cementation surface with glass. Current methods for assessing the fracture resistance of resin-ceramic bonds are marred by uneven stress distribution at the interface, which may result in erroneous interfacial fracture resistance values. We have applied a wedge-loaded double-cantilever-beam testing approach to accurately measure the interfacial fracture resistance of adhesively bonded zirconia-based restorative materials. The interfacial fracture energy GC was determined for adhesively bonded zirconia, graded zirconia and feldspathic ceramic bars. The bonding surfaces were subjected to sandblasting or acid etching treatments. Baseline GC was measured for bonded specimens subjected to 7 days hydration at 37°C. Long-term GC was determined for specimens exposed to 20,000 thermal cycles between 5 and 55°C followed by 2-month aging at 37°C in water. The test data were interpreted with the aid of a 2D finite element fracture analysis. The baseline and long-term GC for graded zirconia was 2-3 and 8 times greater than that for zirconia, respectively. More significantly, both the baseline and long-term GC of graded zirconia were similar to those for feldspathic ceramic. The interfacial fracture energy of feldspathic ceramic and graded zirconia was controlled by the fracture energy of the resin cement while that of zirconia by the interface. GC for the graded zirconia was as large as for feldspathic ceramic, making it an attractive material for use in dentistry. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  7. Effect of sandblasting on surface roughness of zirconia-based ceramics and shear bond strength of veneering porcelain.

    Science.gov (United States)

    He, Min; Zhang, Zutai; Zheng, Dongxiang; Ding, Ning; Liu, Yan

    2014-01-01

    This study aims to investigate the effect of sandblasting on the surface roughness of zirconia and the shear bond strength of the veneering porcelain. Pre-sintered zirconia plates were prepared and divided into four groups. Group A were not treated at all; group B were first sandblasted under 0.2 MPa pressure and then densely sintered; group C and D were sintered first, and then sandblasted under 0.2 MPa and 0.4 MPa pressures respectively. Surface roughness was measured and 3D roughness was reconstructed for the specimens, which were also analyzed with X-ray diffractometry. Finally after veneering porcelain sintering, shear bond tests were conducted. Sandblasting zirconia before sintering significantly increased surface roughness and the shear bond strength between zirconia and veneering porcelain (pveneering porcelain.

  8. Evaluation of translucency of monolithic zirconia and framework zirconia materials

    OpenAIRE

    Tuncel, ?lkin; Turp, I??l; ???mez, Asl?han

    2016-01-01

    PURPOSE The opacity of zirconia is an esthetic disadvantage that hinders achieving natural and shade-matched restorations. The aim of this study was to evaluate the translucency of non-colored and colored framework zirconia and monolithic zirconia. MATERIALS AND METHODS The three groups tested were: non-colored framework zirconia, colored framework zirconia with the A3 shade according to Vita Classic Scale, and monolithic zirconia (n=5). The specimens were fabricated in the dimensions of 15?1...

  9. The efficient removal of endotoxins from insulin using quaternized polyethyleneimine-coated porous zirconia.

    Science.gov (United States)

    McNeff, C; Zhao, Q; Almlöf, E; Flickinger, M; Carr, P W

    1999-10-15

    The synthesis and use of a zirconia-based, alkali-stable strong anion-exchange stationary phase are described for the removal of pyrogenic lipopolysaccharides (LPS) from insulin. The strong anion-exchange material is produced by deposition of polyethyleneimine (PEI) onto porous zirconia particles, followed by cross-linking with a novel reagent, 1,2-bis-(2-iodoethoxy) ethane, and quaternization with iodomethane. Physical characterization of the chromatographic support shows that it has an ion-exchange capacity of 0.6 mmol/g, and 82% of the amine sites on the surface are in quaternized form. Isocratic elution of small benzoic acid derivatives shows good column efficiency. The two primary virtues of this material are its chemical stability under alkali conditions (up to pH 13) and its lower hydrophobicity compared to previously described alkali-stable PEI-coated zirconia supports cross-linked with 1,10-diiododecane. Using this new zirconia-based phase, a purification protocol is developed for the efficient removal of Escherichia coli 0111:B4 LPS from bovine insulin samples. An endotoxin clearance rate of up to 1.3 x 10(8) was attained. Endotoxin levels were reduced to less than 5 endotoxin units/ml even at initial contamination levels as high as 5.0 x 10(6) endotoxin units/ml. Furthermore, endotoxin adsorbed to the porous zirconia column may be easily removed (depyrogenated) using alkali for repeated purification cycles. Copyright 1999 Academic Press.

  10. In vitro performance of implant-supported monolithic zirconia crowns: Influence of patient-specific tooth-coloured abutments with titanium adhesive bases.

    Science.gov (United States)

    Rosentritt, Martin; Rembs, Andreas; Behr, Michael; Hahnel, Sebastian; Preis, Verena

    2015-07-01

    To investigate the influence of the combination of patient-specific abutments and titanium adhesive bases on the long-term in vitro performance of anterior crowns. Ten systems of screw-retained implant and adhesive base combinations (n=8/group) were restored with zirconia or polyetherketone (PEEK) abutments and identical full-anatomical zirconia crowns. For simulating clinical anterior loading, implants were fixed at an angle of 135° and submitted to prolonged thermal cycling and mechanical loading (TC: 6×3000 cycles, 5°C/55°C; ML: 100N, 3.6×10(6) cycles) to cause and register fatigue failure. Failed restorations were examined by means of scanning electron microscopy. Surviving restorations were loaded to fracture. Data (mean±standard deviation) were statistically analyzed (ANOVA; Bonferroni; Kaplan-Meier-Log-Rank; α=0.05). Seven systems survived TCML without any failure. The other three systems showed loosening and fracturing of the screw (0.4-1.6×10(6) loadings) or debonding between base and abutment (0.002-3.4×10(6) loadings). None of the systems showed any fracture of the crown or failed bonding between abutment and crown. The Log-Rank test showed significant (p=0.000) differences. Fracture data significantly varied (ANOVA p=0.000) between the individual systems (minimum: 371N; maximum: 763N). Failures were mostly caused by bending or fracturing of the screw and in three cases by fracture of the abutment. Anterior implant-supported zirconia crowns on titanium adhesive bases and bonded patient-specific zirconia abutments provided good in vitro performance and high fracture resistance. Sufficient high torque moments and early re-screwing may be advised. Most adhesive base and abutment combinations may be appropriate for anterior application. Individual improvements may contribute to enduring success. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Catastrophic failure of a monolithic zirconia prosthesis.

    Science.gov (United States)

    Chang, Jae-Seung; Ji, Woon; Choi, Chang-Hoon; Kim, Sunjai

    2015-02-01

    Recently, monolithic zirconia restorations have received attention as an alternative to zirconia veneered with feldspathic porcelain to eliminate chipping failures of veneer ceramics. In this clinical report, a patient with mandibular edentulism received 4 dental implants in the interforaminal area, and a screw-retained monolithic zirconia prosthesis was fabricated. The patient also received a maxillary complete removable dental prosthesis over 4 anterior roots. At the 18-month follow-up, all of the zirconia cylinders were seen to be fractured, and the contacting abutment surfaces had lost structural integrity. The damaged abutments were replaced with new abutments, and a new prosthesis was delivered with a computer-assisted design and computer-assisted manufacturing fabricated titanium framework with denture teeth and denture base resins. At the 6-month recall, the patient did not have any problems. Dental zirconia has excellent physical properties; however, care should be taken to prevent excessive stresses on the zirconia cylinders when a screw-retained zirconia restoration is planned as a definitive prosthesis. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  12. Zirconia-based versus metal-based single crowns veneered with overpressing ceramic for restoration of posterior endodontically treated teeth: 5-year results of a randomized controlled clinical study.

    Science.gov (United States)

    Monaco, Carlo; Llukacej, Altin; Baldissara, Paolo; Arena, Antonio; Scotti, Roberto

    2017-10-01

    The aim of this 5-year randomized controlled trial was to compare the longevity and clinical behavior of single posterior crowns made with pressable ceramic on zirconia and on metal frameworks, and if failures occur, to delineate the contributing factors. 72 patients, who needed the covering of at least a molar and/or premolar, were included in the study. All teeth were endodontically treated, with absence of periapical lesion or active periodontitis. Ninety single crowns were made with zirconia or metal framework and covered with pressable veneering ceramics. Two independent examiners assessed the survival of restorations at 6 months, 1-4 and 5 years after restoration placement including periapical radiographs, intraoral photographs, and USPHS modified criteria. The statistical analyses were performed with the Kaplan-Meier method. One core fracture occurred in Zircad/Zirpress crowns and one metal ceramic crown was lost for root fracture. Chipping fracture of the veneering ceramic was detected in 2 metal-ceramic crowns and in 3 zirconia-based crowns. The Estimate Cumulative Survival (ECS) and the Estimate Cumulative Success (ECSs) with standard deviation (SE) were respectively 97,73±2,19 and 92,64±4,14 for zirconia-based crowns whereas 97,44±2,39 and 91,11±4,27 for porcelain fused to metal crowns. The present randomized controlled trial shows that the survival of zirconia-based and metal-based single crowns is similar over a follow-up period of 5 years. No significant differences in esthetic, functional and biological outcomes were demonstrated between the two groups. The main failure mode was the chipping fracture of the veneering ceramic in both materials. Study number on ClinicalTrial.gov NCT02758457. According to the results of this clinical study, zirconia-based rehabilitations with overpressing veneering technique represent a valid alternative to metal-based for posterior single crown restorations. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. STABILISED ZIRCONIA

    Directory of Open Access Journals (Sweden)

    LUZ STELLA ARIAS-MAYA

    2014-01-01

    Full Text Available La densificación y la contracción de cerámicos u otros materiales en polvo pueden ser predichos de una manera sencilla usando la curva maestra de sinterizado. En este trabajo se han obtenido los datos de densificación requeridos para construir la curva maestra de sinterizado de zirconia en polvo estabilizada con 3-mol% itria. Se sinterizaron muestras compactadas en frío, así como películas gruesas hechas del mismo polvo y aplicadas a un sustrato rígido. Las pruebas de sinterizado libre y con restricción fueron realizadas aplicando tres velocidades de calentamiento, incluyendo o no una etapa isotérmica a la máxima temperatura de ~1450 °C. La contracción de las muestras se midió durante la densificación usando un dilatómetro de varilla de presión. También se usó un horno convencional, aplicando la misma curva de calentamiento para comparar resultados. El análisis microestructural fue logrado mediante microscopía de barrido electrónico, microscopía de barrido electrónico ambiental y microscopía óptica. Se obtuvo una concordancia aceptable entre muestras similares sinterizadas en el dilatómetro y en el horno convencional, indicando que los datos del dilatómetro pueden ser usados para ambos ambientes. Las muestras que se sinterizaron sin restricción alcanzaron menores densidades que las películas, probablemente debido a que sus densidades iniciales eran menores. Para las muestras libres de restricción, se obtuvo una curva maestra de sinterizado con una energía de activación de 550 kJ mol-1. Para las películas sinterizadas con restricción, algunos problemas asociados con el sustrato y con las incertidumbres de las mediciones impidieron la caracterización de la película, es decir, la obtención de una curva maestra de sinterizado con un solo valor de energía de activación.

  14. Financial Derivatives (Based on Two Supports Evaluation

    Directory of Open Access Journals (Sweden)

    Tiberiu Socaciu

    2016-07-01

    Full Text Available In this paper we build a PDE like Black-Scholes equation in hypothesis of a financial derivative that is dependent on two supports (usual is dependent only on one support, like amoption based on gold, when national currency has a great float.Keywords: Financial derivatives, derivatives evaluation, derivatives based on two supports, extended Itō like lemma.

  15. Zirconia-based crowns up to 5 years in function: a retrospective clinical study and evaluation of prosthetic restorations and failures.

    Science.gov (United States)

    Güncü, M Barιş; Cakan, Umut; Muhtarogullari, Mehmet; Canay, Senay

    2015-01-01

    The purpose of this retrospective study was to evaluate the 5-year clinical performance and failure rate of single- or multiple-unit zirconia-based crowns. A total of 148 patients (39 men and 109 women, mean age: 46.9 ± 10.6 years) treated in university and private practices with 618 single- or multiple-unit zirconia-based (Lava) crowns made on natural teeth from January 2007 to December 2008 were included. Two hundred fifty-nine anterior and 359 posterior crowns were examined. A core and/or veneer fracture that required replacement of the restoration was considered to be a failure. The cumulative survival rate (CSR) was described with Kaplan-Meier survival functions. The crowns replaced for other reasons were deemed lost to follow-up, and esthetic, functional, and biologic complications were rated. At the 5-year follow-up, no zirconia core fractures were observed. Twelve veneer fractures that required crown replacement were detected. The CSR was 98.1%. There was a statistically significant difference between survival of the anterior and posterior restorations (P crowns experienced biologic and technical complications. The most common complications were smooth veneer fracture (4, 0.6%), loss of retention (7, 1%), staining because of smoking (24, 4%), and gingival recession (48, 8%). According to the 5-year CSR (98.1%) observed in this study, zirconia-based single or multiple crowns may be considered an acceptable treatment modality for the replacement of anterior and posterior teeth. RESULTS from the current study should be supported by additional randomized clinical trials.

  16. Investigating Zirconia Catalysts = Handling Sensitive Materials

    OpenAIRE

    Klose, Barbara S.; Jentoft, Rolf E.; Hahn, Alexander H. P.; Ressler, Thorsten; Yang, Xiaobo; Jentoft, Friederike C.

    2003-01-01

    Investigating Zirconia Catalysts = Handling Sensitive Materials B.S. Klose, R.E. Jentoft, A. Hahn, T. Ressler, X. Yang, F.C. Jentoft Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Society Faradayweg 4-6, D-14195 Berlin, Germany Introduction Sulfated zirconia (SZ) based catalysts are active for n-butane isomerization at 373 K [1]. Despite intense research, no convincing structure-activity relationship for these materials has evolved. Still in question...

  17. A practice-based clinical evaluation of the survival and success of metal-ceramic and zirconia molar crowns: 5-year results.

    Science.gov (United States)

    Rinke, S; Kramer, K; Bürgers, R; Roediger, M

    2016-02-01

    This practice-based study evaluates the survival and success of conventionally luted metal-ceramic and zirconia molar crowns fabricated by using a prolonged cooling period for the veneering porcelain. Fifty-three patients were treated from 07/2008 to 07/2009 with either metal-ceramic crowns (MCC) or zirconia crowns (ZC). Forty-five patients (26 female) with 91 restorations (obser-vational period: 64.0 ± 4.8 months) participated in a clinical follow-up examination and were included in the study. Estimated cumulative survival (ECSv), success (ECSc) and veneering ceramic success (ECVCSc) were calculated (Kaplan-Meier) and analysed by the crown fabrication technique and the position of the restoration (Cox regression model) (P crowns placed on tooth-neighboured abutments (n = 47), (5-year VCF-rate: 4.3%). In the present study, zirconia molar crowns demonstrated a 5-year ECSv, ECSc and ECVCSc comparable to MCCs. Irrespective of the fabrication technique, crowns on terminal abutments bear a significantly increased risk for VCFs. Clinical investigations with an increased number of restorations are needed. © 2015 John Wiley & Sons Ltd.

  18. Fundamental aspects of Am and Cm in zirconia-based materials. Investigations using X-ray diffraction and Raman spectroscopy

    International Nuclear Information System (INIS)

    Raison, P.E.; Haire, R.G.; Assefa, Z.

    2002-01-01

    We have investigated incorporation of americium and curium in selected zirconia-based materials. Fundamental aspects were explored via X-ray diffraction and Raman spectroscopy. First explored was the pseudo ternary system, AmO 2 -ZrO 2 -Y 2 O 3 . It was found that stable, cubic solid solutions (Am x Zr 1-x Y y )O 2-2/y can be obtained for selected compositions. The cell parameters of the cubic phases were established as being linear with the AmO 2 content. For the Cm 2 O 3 -ZrO 2 system, it was determined that diphasic materials are produced, except for two compositions: 25 mol% and 50 mol% of CmO 1.5 . For these compositions a single-phase cubic fluorite type solid solution (a=5.21A±0.01) and a pyrochlore oxide Cm 2 Zr 2 O 7 (a=10.63A±0.02) are formed, respectively. The stability of pyrochlore oxides is also being investigated as a function of self-irradiation, using shorter-lived isotopes, one being the californium pyrochlore 249 Cf 2 Zr 2 O 7 . We obtained evidence that after six months of storage the pyrochlore oxide is undergoing structural change. Additional studies are in progress. (author)

  19. Characterisation and fabrication of zirconia and thoria based ceramics for nuclear applications

    International Nuclear Information System (INIS)

    Barrier, D.C.

    2005-11-01

    The reduction of the long term radiotoxicity of nuclear waste during disposal is the aim of the research called ''Partitioning and Transmutation of Minor actinides (MAs)'', which also requires the development of inert ceramic support materials. Moreover, after separation, if the transmutation is not available, the actinides can be conditioned into stable dedicated solid matrices (Partitioning and Conditioning strategy). Yttrium-stabilized zirconia and thoria are discussed in the international nuclear community as candidates for the fixation of long-lived actinides as target material for transmutation and as stable materials for long-term final disposal. The aims of the following work are twofold: determine the impact of the addition of actinides, simulated by cerium on the properties of the matrices and study the possibility of synthesising homogeneous ceramics using simple fabrication routes. Within this framework, (ZrY)O 2-x -CeO 2 and ThO 2 -CeO 2 powders with variable ceria contents (from 0 to 100 %) were synthesised by a co-precipitation method of nitrate solution. The influence of ceria concentration on the powder' properties, such as thermal behaviour and the evolution of material crystallisation during annealing, was investigated in detail by thermogravimetry (TG) coupled with differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Both systems crystallise at high temperature in a stable solid solution, fcc, fluorite type structure and follow the Vegard's law for the complete range of ceria. For both systems a critical concentration of 20 mol% has been established. For ceria concentrations lower than 20%, the properties of the system are mainly controlled by the matrix. Pellets with different ceria concentrations were compacted from these powders by using different technological cycles. In order to obtain materials with reliable properties, the technological parameters of each chosen fabrication route, have been optimised. By employing mild wet

  20. Characterisation and fabrication of zirconia and thoria based ceramics for nuclear applications

    Energy Technology Data Exchange (ETDEWEB)

    Barrier, D.C.

    2005-11-01

    The reduction of the long term radiotoxicity of nuclear waste during disposal is the aim of the research called ''Partitioning and Transmutation of Minor actinides (MAs)'', which also requires the development of inert ceramic support materials. Moreover, after separation, if the transmutation is not available, the actinides can be conditioned into stable dedicated solid matrices (Partitioning and Conditioning strategy). Yttrium-stabilized zirconia and thoria are discussed in the international nuclear community as candidates for the fixation of long-lived actinides as target material for transmutation and as stable materials for long-term final disposal. The aims of the following work are twofold: determine the impact of the addition of actinides, simulated by cerium on the properties of the matrices and study the possibility of synthesising homogeneous ceramics using simple fabrication routes. Within this framework, (ZrY)O{sub 2-x}-CeO{sub 2} and ThO{sub 2}-CeO{sub 2} powders with variable ceria contents (from 0 to 100 %) were synthesised by a co-precipitation method of nitrate solution. The influence of ceria concentration on the powder' properties, such as thermal behaviour and the evolution of material crystallisation during annealing, was investigated in detail by thermogravimetry (TG) coupled with differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Both systems crystallise at high temperature in a stable solid solution, fcc, fluorite type structure and follow the Vegard's law for the complete range of ceria. For both systems a critical concentration of 20 mol% has been established. For ceria concentrations lower than 20%, the properties of the system are mainly controlled by the matrix. Pellets with different ceria concentrations were compacted from these powders by using different technological cycles. In order to obtain materials with reliable properties, the technological parameters of each chosen fabrication

  1. Beberapa Penggunaan Zirconia Dalam Bidang Kedokteran Gigi

    OpenAIRE

    Afifuddin

    2008-01-01

    Salah satu bentuk kemajuan dalam bidang kedokteran gigi adalah penggunaan zirconia sebagai dental material. Zirconia berasal dari unsur zirconium (Zr) yang memiliki nomor atom 40 dan berat atom 91,22. Zirconia merupakan keramik bioinert. Ada beberapa tipe dari zirconia, yaitu ; tetragonal zirconia polycrystals (TZP), fully stabilized zirconia (FSZ), partially stabilized zirconia (PSZ), zirconia toughened alumina (ZTA), dan transformation toughened zirconia (TTZ). Tetapi yang dipakai sebagai d...

  2. Structural and Chemical Analysis of the Zirconia-Veneering Ceramic Interface.

    Science.gov (United States)

    Inokoshi, M; Yoshihara, K; Nagaoka, N; Nakanishi, M; De Munck, J; Minakuchi, S; Vanmeensel, K; Zhang, F; Yoshida, Y; Vleugels, J; Naert, I; Van Meerbeek, B

    2016-01-01

    The interfacial interaction of veneering ceramic with zirconia is still not fully understood. This study aimed to characterize morphologically and chemically the zirconia-veneering ceramic interface. Three zirconia-veneering conditions were investigated: 1) zirconia-veneering ceramic fired on sandblasted zirconia, 2) zirconia-veneering ceramic on as-sintered zirconia, and 3) alumina-veneering ceramic (lower coefficient of thermal expansion [CTE]) on as-sintered zirconia. Polished cross-sectioned ceramic-veneered zirconia specimens were examined using field emission gun scanning electron microscopy (Feg-SEM). In addition, argon-ion thinned zirconia-veneering ceramic interface cross sections were examined using scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectrometry (EDS) at high resolution. Finally, the zirconia-veneering ceramic interface was quantitatively analyzed for tetragonal-to-monoclinic phase transformation and residual stress using micro-Raman spectroscopy (µRaman). Feg-SEM revealed tight interfaces for all 3 veneering conditions. High-resolution transmission electron microscopy (HRTEM) disclosed an approximately 1.0-µm transformed zone at sandblasted zirconia, in which distinct zirconia grains were no longer observable. Straight grain boundaries and angular grain corners were detected up to the interface of zirconia- and alumina-veneering ceramic with as-sintered zirconia. EDS mapping disclosed within the zirconia-veneering ceramic a few nanometers thick calcium/aluminum-rich layer, touching the as-sintered zirconia base, with an equally thick silicon-rich/aluminum-poor layer on top. µRaman revealed t-ZrO2-to-m-ZrO2 phase transformation and residual compressive stress at the sandblasted zirconia surface. The difference in CTE between zirconia- and the alumina-veneering ceramic resulted in residual tensile stress within the zirconia immediately adjacent to its interface with the veneering ceramic. The rather minor chemical

  3. In vitro effects of zirconia and alumina particles on human blood monocyte-derived macrophages: X-ray microanalysis and flow cytometric studies.

    Science.gov (United States)

    Nkamgueu, E M; Adnet, J J; Bernard, J; Zierold, K; Kilian, L; Jallot, E; Benhayoune, H; Bonhomme, P

    2000-12-15

    The cytocompatibility of two particulate bioceramics, zirconia and alumina, was studied using human blood monocytes driven to differentiate into mature macrophages with granulocyte macrophage-colony-stimulating factor. Changes in individual cell elemental composition, particularly sodium and potassium content, were assessed by X-ray microanalysis of ultrathin freeze-dried sections. Phagocytosis and respiratory burst of macrophages exposed to biomaterial for 7 days were analyzed under flow cytometry using uptake of fluorescent latex beads and 2'7'-dichlorofluorescien diacetate oxidation, respectively. Zirconia and alumina particles were found to decrease the intracellular potassium/sodium ratio (an index of cell vitality) significantly (p2 times reduced by zirconia and >5 times reduced by alumina). The present study clearly demonstrates that reduction of the phagocytic capacity of macrophages associated with altered oxidative metabolism caused by biomaterial particles is characterized by changes in intracellular elemental content. Thus, investigation of cellular homeostasis by electron probe microanalysis together with analysis of functional changes may improve estimation of biomaterial cytocompatibility. Copyright 2000 John Wiley & Sons, Inc.

  4. Effects of cementation surface modifications on fracture resistance of zirconia

    Science.gov (United States)

    Srikanth, Ramanathan; Kosmac, Tomaz; Bona, Alvaro Della; Yin, Ling; Zhang, Yu

    2015-01-01

    Objectives To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Methods Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 mm or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2 mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Results Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. Significance While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. PMID:25687628

  5. Effects of cementation surface modifications on fracture resistance of zirconia.

    Science.gov (United States)

    Srikanth, Ramanathan; Kosmac, Tomaz; Della Bona, Alvaro; Yin, Ling; Zhang, Yu

    2015-04-01

    To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  6. 40 CFR 1065.284 - Zirconia (ZrO2) analyzer.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Zirconia (ZrO2) analyzer. 1065.284... Zirconia (ZrO2) analyzer. (a) Application. You may use a zirconia (ZrO2) analyzer to measure air-to-fuel...O2-based system must meet the linearity verification in § 1065.307. You may use a Zirconia analyzer...

  7. Influence of framework color and layering technique on the final color of zirconia veneered restorations

    NARCIS (Netherlands)

    Aboushelib, M.N.; Dozic, A.; Liem, J.K.

    2010-01-01

    Objective: To investigate the influence of colored zirconia frameworks on the overall color match of zirconia- veneered restorations. Method and Materials: Identical natural and colored zirconia frameworks (Cercon Base, Degudent) were layered using a veneer ceramic (IPS e.max Ceram Dentin, Ivoclar

  8. Bonding to zirconia using a new surface treatment

    NARCIS (Netherlands)

    Aboushelib, M.N.; Feilzer, A.J.; Kleverlaan, C.J.

    2010-01-01

    Purpose: Selective infiltration etching (SIE) is a newly developed surface treatment used to modify the surface of zirconia-based materials, rendering them ready for bonding to resin cements. The aim of this study was to evaluate the zirconia/resin bond strength and durability using the proposed

  9. What Is in Your Zirconia?

    Science.gov (United States)

    Helvey, Gregg A

    2017-04-01

    The immense popularity of zirconia as an indirect restorative material in dentistry has led to seemingly countless numbers of companies selling zirconia discs and blocks. The reliability of zirconia, however, is subject to specific manufacturing and processing protocols. Thus, it is of paramount importance for any dental professional utilizing zirconia to be aware of the source of the material and the various factors that can affect the success or failure of a final restoration. This article discusses the journey of zirconia, from being found among the elements of the earth to being placed in the patient's mouth. It also touches on drawbacks, such as translucency, associated with zirconia.

  10. Marginal gap, cement thickness, and microleakage of 2 zirconia crown systems luted with glass ionomer and MDP-based cements.

    Science.gov (United States)

    Sener, Isil; Turker, Begum; Valandro, Luiz Felipe; Ozcan, Mutlu

    2014-01-01

    This in vitro study evaluated the marginal gap, cement thickness, and microleakage of glass-ionomer cement (GIC) and phosphate monomer-containing resin cement (MDP-RC) under 2 zirconia crown systems (Cercon and DC-Zirkon). Forty human premolars were prepared for all-ceramic zirconia crowns with a 1 mm circumferential finish line and a 1.5 mm occlusal reduction. The crowns (n = 10 per group) from each zirconia system were randomly divided into 2 groups and cemented either with GIC (Vivaglass CEM) or MDP-RC (Panavia F 2.0) cement. The cemented crowns were thermocycled 5000 times (5°-55°C). The crowns were immersed in 0.5% basic fuchsine dye solution for 24 hours and sectioned buccolingually and mesiodistally. Specimens were examined under optical microscope (100X). Data were analyzed using Student t-test and chi-square tests (α = 0.05). Mean marginal gap values for Cercon (85 ± 11.4 μm) were significantly higher than for DC-Zircon (75.3 ± 13.2 μm) (P = 0.018). The mean cement thickness values of GIC (81.7 ± 13.9 μm) and MDP-RC (78.5 ± 12.5 μm) were not significantly different (P = 0.447). Microleakage scores did not demonstrate significant difference between GIC (P = 0.385) and MDP-RC (P = 0.631) under Cercon or DC-Zircon. Considering the cement thickness values and microleakage scores obtained, both zirconia crown systems could be cemented in combination with either GIC or MDP-RC.

  11. Application of zirconia modified with KOH as heterogeneous solid base catalyst to new non-edible oil for biodiesel

    International Nuclear Information System (INIS)

    Takase, Mohammed; Zhang, Min; Feng, Weiwei; Chen, Yao; Zhao, Ting; Cobbina, Samuel J.; Yang, Liuqing; Wu, Xiangyang

    2014-01-01

    Highlights: • Silybum marianum contain high amount of oil (46%) and Linoleic acids (65.68%). • Incipient wetness impregnation method was used to load KOH on ZrO 2. • KOH(32%)/ZrO 2 -5 was used to transesterificate Silybum marianum to biodiesel. • Conversion yield of triglycerides to biodiesel (90.8%) at 60 °C was obtained in 2 h. • The properties of the biodiesel were comparable to international standards. - Abstract: This study seeks to investigate zirconia modified with KOH as heterogeneous solid base catalyst for transesterification of new non-edible, Silybum marianum (oil content 46%, FFA 0.68% and linoleic acid 65.68%) oil using methanol to biodiesel. Having screened the catalytic performance of ZrO 2 loaded with different K-compounds, 32% KOH loaded on ZrO 2 was chosen. The catalyst was prepared using incipient wetness impregnation method. Following drying (after impregnation) and calcination at 530 °C for 5 h, the catalyst was characterized by means of Hammett indicators, XRD, FTIR, SEM, TGA and N 2 adsorption desorption measurements. It was found that the yield of the fatty acid methyl esters (FAME) was related to the catalyst base strength. The catalyst had granular and porous structures with high basicity and superior catalytic performance for the transesterification reaction. Maximum yield (90.8%) was obtained at 15:1 methanol to oil molar ratio, 6% catalyst amount, 60 °C reaction temperature in 2 h. The catalyst maintained sustained activity after five times of usage. The oxidative stability and iodine value were the only unsuitable properties of the biodiesel (out of range) but can easily be improved. The cetane number, flash point and the cold flow properties among others were however, comparable to international standards. The study indicated that KOH(32%)/ZrO 2 -5 is an economically, suitable catalyst for producing biodiesel from S. marianum oil which is a potential new non-edible feedstock that can contribute positively to biodiesel

  12. Nanocomposite thin films of gold nanoparticles embedded in yttria-stabilized zirconia for plasmonic-based harsh environment gas detection

    Science.gov (United States)

    Rogers, Phillip H.

    Increased health concerns due to the emission of gases linked to the production of tropospheric ozone by petroleum based fuel burning engines has resulted in the codification of more stringent emissions regulations domestically. Emissions regulations on commercial jetliners are one of the areas to be met with stricter standards. Currently there is not a sensing technology that can detect the emissions gases in the exhaust stream of a jet turbine engine with lower detection limits that meet these standards. The localized surface plasmon resonance (LSPR) of noble metal nanoparticles embedded in dielectric matrices is an optical response that can be extremely sensitive to many environmental parameters. Nanocomposites of Au nanoparticles embedded in yttria-stabilized zirconia (Au-YSZ) are an ideal case study for these plasmonic materials. Using a metal oxide matrix with oxygen ion vacancies, such as YSZ, allows one to finely tune the local environmental charge of the embedded metal nanoparticles upon varying the oxygen and hydrogen content of the gas exposure mixture. After gas exposure data is collected in the form of optical absorption spectra, the LSPR spectra due to the Au nanoparticles embedded in the YSZ matrix undergo automated Lorentzian and Drude model fitting for calculating fundamental charge exchange and plasmonic dampening effects versus gas exposure concentration. These titration experiments have been performed for Au-YSZ nanocomposites exposed to O2, H2, NO 2, and CO in N2 backgrounds at 500°C and equilibrium data has been acquired for both the average charge per Au nanoparticle and the scattering frequency of the plasmons over a variety of exposure conditions. One paramount result made possible by this plasmonic based gas detection by Au-YSZ nanocomposite thin films was a repeatable 5 ppm lower detection limit towards NO2 in air at 500°C. In comparing the charge exchange observed using both the fitted exposure data and an electrochemical model

  13. Damage Maps of Veneered Zirconia under Simulated Mastication

    Science.gov (United States)

    Kim, Jae-Won; Kim, Joo-Hyung; Janal, Malvin N.; Zhang, Yu

    2016-01-01

    Zirconia based restorations often fracture from chipping and/or delamination of the porcelain veneers. We hypothesize that veneer chipping/delamination is a result of the propagation of near-contact induced partial cone cracks on the occlusal surface under mastication. Masticatory loading involves the opposing tooth sliding along the cuspal inner incline surface with an applied biting force. To test this hypothesis, flat porcelain veneered zirconia plates were cemented to dental composites and cyclically loaded (contact–slide–liftoff) at an inclination angle as a simplified model of zirconia based restorations under occlusion. In the light of in-situ observation of damage evolution in a transparent glass/zirconia/polycarbonate trilayer, postmortem damage evaluation of porcelain/zirconia/composite trilayers using a sectioning technique revealed that deep penetrating occlusal surface partial cone fracture is the predominant fracture mode of porcelain veneers. Clinical relevance is discussed. PMID:19029080

  14. Stability of Ni–yttria stabilized zirconia anodes based on Ni-impregnation

    DEFF Research Database (Denmark)

    Klemensø, Trine; Thydén, Karl Tor Sune; Chen, Ming

    2010-01-01

    Sintering of Ni is a key stability issue for Ni–YSZ anodes, and especially infiltration based electrodes. The potential of MgO, Al2O3, TiO2, CeO2 and Ce0.90Gd0.10O1.95 (CGO10) as sintering inhibitors was investigated for infiltrated Ni based anode structures. The structures were prepared from tap...

  15. Calcium Oxide Supported on Monoclinic Zirconia as a Highly Active Solid Base Catalyst

    NARCIS (Netherlands)

    Frey, A.M.; Haasterecht, van T.; Jong, de K.P.; Bitter, J.H.

    2013-01-01

    Calcium oxide supported on ZrO2 is a highly active catalyst for base-catalyzed reactions such as aldol-type reactions and transesterification reactions. The role of key parameters during preparation, that is, impregnation versus precipitation, heat treatment, and metal oxide loading on the basicity

  16. Surface modification of zirconia-based bioceramics for orthopedic and dental applications

    OpenAIRE

    Flamant, Quentin

    2016-01-01

    Debido a sus excelentes propiedades mecánicas y una excelente biocompatibilidad, el uso de las cerámicas de base de circona en aplicaciones dentales y ortopédicas ha crecido rápidamente durante las últimas décadas. Sin embargo, tanto la alúmina como la circona son bioinertes, lo cual dificulta su implantación en contacto directo con el hueso. Además, las infecciones siguen siendo una de las principales causas de fallo de implantes. Para resolver ambos problemas, se requiere un mejor diseño de...

  17. Translucence in dental prosthesis based on zirconia ceramics: effect of the sintering parameters; Translucidez em proteses dentarias a base de zirconia estabilizada com itria: efeito dos parametros de sinterizacao

    Energy Technology Data Exchange (ETDEWEB)

    Santos, C., E-mail: claudinei@demar.eel.usp.br [Universidade de Sao Paulo (USP), Lorena, SP (Brazil). Escola de Engenharia; Costa, L.; Habibe, R.H.; Souza, J.V.C.; Habibe, C.H. [Centro Universitario de Volta Redonda (MeMAT/UNIFOA), RJ (Brazil). Pro-Reitoria de Pesquisa e Extensao; Silva, O.M.M. [Centro Tecnico Aeroespacial (CTA/IAE/AMR), Sao Jose dos Campos, SP (Brazil)

    2011-07-01

    In this work the translucence of Zirconia dental ceramics was evaluated as function of sintering conditions (temperature and isothermal holding time). Samples with 15x15x1mm, were sintered at 1450 to 1600 deg C, with holding of 2h or 4h. Sintered samples were characterized by relative density, crystalline phases and microstructural aspects. Full density was obtained in samples sintered at 1530 and 1600 deg C, which presented higher grain sizes. Na increasing of translucence was observed in samples sintered at 1530 and 1600, correlating these properties with increasing of density and grain size of the samples. (author)

  18. Zirconia based ceramic coating on a metal with plasma electrolytic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Akatsu, T; Shinoda, Y; Wakai, F [Secure Materials Center, Materials and Structures Laboratory, Tokyo Institute of Technology, 4259-R3-24, Nagatsuta, Midori, Yokohama (Japan); Kato, T, E-mail: akatsu.t.aa@m.titech.ac.jp [Department of Materials Science and Engineering, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259-R3-24, Nagatsuta, Midori, Yokohama (Japan)

    2011-10-29

    We challenge to fabricate a thermal barrier coating (TBC) made of ZrO{sub 2} based ceramics on a Ni based single crystal superalloy with plasma electrolytic oxidation (PEO) by incorporating metal species from electrolyte into the coating. The PEO process is carried out on the superalloy galvanized with aluminium for 15min in Na{sub 4}O{sub 7}P{sub 4} solution for an oxygen barrier coating (OBC) and is followed by PEO in K{sub 2}[Zr(CO{sub 3}){sub 2}(OH){sub 2}] solution for TBC. We obtained the following results; (1) Monoclinic-, tetragonal-, cubic-ZrO{sub 2} crystals were detected in TBC. (2) High porosity with large pores was observed near the interface between OBC and TBC. The fine grain structure with a grain size of about 300nm was typically observed. (3) The adhesion strength between PEO coatings and substrate was evaluated to be 26.8{+-}6.6MPa. At the adhesion strength test, PEO coatings fractured around the interface between OBC and TBC. The effect of coating structure on adhesion strength is explained through the change in spark discharge during PEO process.

  19. Zirconia-reinforced dental restorations

    NARCIS (Netherlands)

    Chen, C.

    2013-01-01

    The series of studies conducted in this thesis showed that there are several ways to enhance the performance of fixed restorations regarding the application of zirconia. One possible way is to change the sintering procedure of zirconia, so that the physical properties of zirconia such BFS, density

  20. DLTS Analysis and Interface Engineering of Solution Route Fabricated Zirconia Based MIS Devices Using Plasma Treatment

    Science.gov (United States)

    Kumar, Arvind; Mondal, Sandip; Koteswara Rao, K. S. R.

    2018-02-01

    In this work, we have fabricated low-temperature sol-gel spin-coated and oxygen (O2) plasma treated ZrO2 thin film-based metal-insulator-semiconductor devices. To understand the impact of plasma treatment on the Si/ZrO2 interface, deep level transient spectroscopy measurements were performed. It is reported that the interface state density ( D it) comes down to 7.1 × 1010 eV-1 cm-2 from 4 × 1011 eV-1 cm-2, after plasma treatment. The reduction in D it is around five times and can be attributed to the passivation of oxygen vacancies near the Si/ZrO2 interface, as they try to relocate near the interface. The energy level position ( E T) of interfacial traps is estimated to be 0.36 eV below the conduction band edge. The untreated ZrO2 film displayed poor leakage behavior due to the presence of several traps within the film and at the interface; O2 plasma treated films show improved leakage current density as they have been reduced from 5.4 × 10-8 A/cm2 to 1.98 × 10-9 A/cm2 for gate injection mode and 6.4 × 10-8 A/cm2 to 6.3 × 10-10 A/cm2 for substrate injection mode at 1 V. Hence, we suggest that plasma treatment might be useful in future device fabrication technology.

  1. On the lateral response of zirconia

    Science.gov (United States)

    Appleby-Thomas, Gareth; Wood, David; Goff, Michael; Millett, Jeremy; Painter, Jonathan

    2017-06-01

    Zirconia-based (partially stabilised zirconia oxide, PSZ) ceramics have high strengths and densities; they have consequently found an extensive niche as wear-resistant materials. Their high impedance can also be of particular use in shock loading applications where high pressures are required in cases where non-metallic impactors are needed (for example, to avoid magnetic effects on diagnostics). However, despite their prevalence, there is a relative paucity of data on these materials in the literature. In particular, there is a lack of significant information available on the evolution of shear strength under shock. Consequently in this study, the lateral response of a series of zirconia targets is investigated under a variety of impact conditions. A member of the Institute of Physics (Reciprocal Membership - no. 1136154).

  2. Effect of a zirconia primer on the push-out bond strength of zirconia ceramic posts to root canal dentin.

    Science.gov (United States)

    Torabi Ardakani, Mahshid; Giti, Rashin; Taghva, Masume; Javanmardi, Samane

    2015-09-01

    The retention of zirconia ceramic posts to root canal dentin with resin-based luting cements is relatively poor. The purpose of this in vitro study was to evaluate the effect of a new zirconia primer, a mixture of organophosphate and carboxylic acid monomers, on the push-out bond strength of zirconia posts to root canal dentin. The root canals of 40 extracted human maxillary central incisors were endodontically treated and the post spaces were prepared. Zirconia posts were luted with 2 different resin luting agents (Panavia F and Clearfil SA luting cements) with and without the zirconia primer (Z-Prime Plus; Bisco). Three segments, each 2 mm high, were cut perpendicular to the post from each root. Bond strength was determined by pushing out the post with a universal testing machine. Three-way ANOVA and the Tukey HSD test was used to assess the effects of the zirconia primer, the 2 different resin luting cements, and different thirds of the root canal (α=.05). The zirconia primer significantly increased the push-out bond strength of zirconia posts to root canal dentin. Clearfil SA luting cement provided significantly higher bond strength than did Panavia F. For all experimental groups combined, bond strength decreased from the coronal to the apical section. A zirconia primer based on organophosphate/carboxylic acid monomers increased the bond strength of zirconia posts to root canal dentin bonded with both resin luting cements. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  3. In vitro performance of full-contour zirconia single crowns.

    Science.gov (United States)

    Beuer, Florian; Stimmelmayr, Michael; Gueth, Jan-Frederik; Edelhoff, Daniel; Naumann, Michael

    2012-04-01

    Zirconia based restorations exhibited high failure rates due to veneering-porcelain fractures. Milling to full-contour might be an alternative approach for zirconia restorations. The aim of this study was to evaluate full-contour zirconia crowns in terms of light-transmission, contact wear (restoration and antagonist) and load-bearing capacity. Powder build-up veneered zirconia substructures and CAD/CAM-veneered zirconia substructures served as controls. Four different kinds of crowns were fabricated on 12 metal dies: zirconia substructure with powder build-up porcelain (veneering technique), zirconia substructure with CAD/CAM generated veneering (sintering technique), full-contour zirconia glazed (glazed full-contour) and full-contour zirconia polished (polished full-contour). All crowns had the same dimensions. After light-transmission was measured the crowns were cemented on the corresponding metal dies. The specimens were loaded according to a special wear method in the chewing simulator (120,000 mechanical cycles, 5 kg load, 0.7 mm sliding movement, 320 thermocycles). Wear of the restoration and the antagonist were measured. All specimens were loaded until failure. One-way ANOVA and a LSD post-hoc test were used to compare data at a level of 5%. Polished full-contour showed significantly higher light transmission than the other groups (p=0.003; ANOVA). Polished full-contour exhibited significantly less contact wear at the restoration (p=0.01; ANOVA) and higher contact wear at the antagonist (p=0.016; ANOVA) compared to the other groups. Glazed full-contour zirconia showed similar contact wear at the antagonist compared to veneering technique (p=0.513, post-hoc LSD). Crowns with conventional veneering showed significantly lower load-bearing capacity (pzirconia to full-contour with glazed surface might be an alternative to traditionally veneered restorations. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. Derivation of GFDM Based on OFDM Principles

    Energy Technology Data Exchange (ETDEWEB)

    Hussein Moradi; Behrouz Farhang-Boroujeny

    2015-06-01

    This paper starts with discussing the principle based on which the celebrated orthogonal frequency division multiplexing (OFDM) signals are constructed. It then extends the same principle to construct the newly introduced generalized frequency division multiplexing (GFDM) signals. This novel derivation sheds light on some interesting properties of GFDM. In particular, our derivation seamlessly leads to an implementation of GFDM transmitter which has significantly lower complexity than what has been reported so far. Our derivation also facilitates a trivial understanding of how GFDM (similar to OFDM) can be applied in MIMO channels.

  5. Effect of conditioning methods on the microtensile bond strength of phosphate monomer-based cement on zirconia ceramic in dry and aged conditions

    NARCIS (Netherlands)

    Amaral, Regina; Ozcan, Mutlu; Valandro, Luiz Felipe; Balducci, Ivan; Bottino, Marco Antonio

    The objective of this study was to evaluate the durability of bond strength between a resin cement and aluminous ceramic submitted to various surface conditioning methods. Twenty-four blocks (5 X 5 X 4 mm 3) of a glass-in filtrated zirconia-alumina ceramic (inCeram Zirconia Classic) were randomly

  6. Microtensile bond strength of a resin cement to glass infiltrated zirconia-reinforced ceramic : The effect of surface conditioning

    NARCIS (Netherlands)

    Amaral, R; Ozcan, M; Bottino, MA; Valandro, LF

    Objectives. This study evaluated the effect of three surface conditioning methods on the microtensile bond strength of resin cement to a glass-infiltrated zirconia-reinforced alumina-based core ceramic. Methods. Thirty blocks (5 x 5 x 4 mm) of In-Ceram Zirconia ceramics (In-Ceram Zirconia-INC-ZR,

  7. Microtensile bond strength of a resin cement to glass infiltrated zirconia-reinforced ceramic: The effect of surface conditioning

    NARCIS (Netherlands)

    Amaral, R.; Ozcan, M.; Bottino, M.A.; Valandro, L.F.

    2006-01-01

    Objectives. This study evaluated the effect of three surface conditioning methods on the microtensile bond strength of resin cement to a glass-infiltrated zirconia-reinforced alumina-based core ceramic. Methods. Thirty blocks (5 x 5 x 4 mm) of In-Ceram Zirconia ceramics (In-Ceram Zirconia-INC-ZR,

  8. Fixed Dental Prostheses and Single-Tooth Crowns Based on Ceria-Stabilized Tetragonal Zirconia/Alumina Nanocomposite Frameworks: Outcome After 2 Years in a Clinical Trial.

    Science.gov (United States)

    Hüttig, Fabian; Keitel, Jan P; Prutscher, Andreas; Spintzyk, Sebastian; Klink, Andrea

    This clinical trial tested bilayered restorations based on ceria-stabilized tetragonal zirconia/alumina frameworks veneered with feldspathic ceramic. A total of 67 crowns and 40 fixed dental prostheses (FDPs) were luted in 57 patients with self-etching/self-adhesive composite resin cement. Dental status and integrity of restorations were evaluated at 2 weeks, 6 months, and then annually. A total of 66 crowns and 36 FDPs (88% posterior) survived for success rates of 93.4% for crowns and 89% for FDPs at 2 years. In particular, 11 cohesive ceramic chippings were observed in 5 crowns and 6 FDPs. The material allows excellent marginal adaptation. Susceptibility to veneering failures might be due to framework design and the necessities of esthetics.

  9. Influence of Light Irradiation Through Zirconia on the Degree of Conversion of Composite Cements.

    Science.gov (United States)

    Inokoshi, Masanao; Pongprueksa, Pong; De Munck, Jan; Zhang, Fei; Vanmeensel, Kim; Minakuchi, Shunsuke; Vleugels, Jozef; Naert, Ignace; Van Meerbeek, Bart

    2016-01-01

    To assess the light irradiance (LI) delivered by two light-curing units and to measure the degree of conversion (DC) of three composite cements and one flowable composite when cured through zirconia or ceramic-veneered zirconia plates with different thicknesses. Three dual-curing composite cements (Clearfil Esthetic Cement, Panavia F2.0, G-CEM LinkAce) and one light-curing flowable composite (G-aenial Universal Flo) were investigated. Nine different kinds of zirconia plates were prepared from three zirconia grades (YSZ: Aadva and KATANA; Ce-TZP/Al2O3: NANOZR) in three different thicknesses (0.5- and 1.5-mm-thick zirconia, and 0.5-mm-thick zirconia veneered with a 1.0-mm-thick veneering ceramic). Portions of the mixed composite cements and the flowable composite were placed on a light spectrometer to measure LI while being light cured through the zirconia plates for 40 s using two light-curing units (n = 5). After light curing, micro-Raman spectra of the composite films were acquired to determine DC at 5 and 10 min, 1 and 24 h, and at 1 week. The zirconia grade and the thickness of the zirconia/veneered zirconia plates significantly decreased LI. Increased LI did not increase DC. Only the Ce-TZP/Al2O3 (NANOZR) zirconia was too opaque to allow sufficient light transmission and resulted in significantly lower DC. Although zirconia-based restorations attenuate the LI of light-curing units, the composite cements and the flowable composite could be light cured through the YSZ zirconia. LI is too low through Ce-TZP/Al2O3 zirconia, necessitating the use of self-/dual-curing composite cements.

  10. Optical characterization and Judd-Ofelt analysis of Pr3+ ions in sol-gel derived zirconia/polyethylene glycol composite

    Science.gov (United States)

    Jose, Saritha K.; Gopi, Subash; Thomas, Vinoy; Sreeja, E.; Joseph, Cyriac; Unnikrishnan, N. V.; Biju, P. R.

    2018-02-01

    The photoluminescence characteristics of praseodymium (Pr3+) doped zirconia/polyethylene glycol (ZrO2/PEG) samples were studied using optical absorption and emission spectra. The optical properties were theoretically analysed using standard and modified Judd-Ofelt (J-O) models. The oscillator strength of the observed transitions and J-O intensity parameters were calculated using these J-O models. The radiative properties such as radiative transition probability (AT), branching ratio (βR), stimulated emission cross-section (σe) and gain band width (σe × Δλeff) for the excited states of Pr3+ in ZrO2/PEG composite have been determined. The experimental branching ratios obtained from the emission spectra were compared with the theoretical values. The excitation spectra of Pr3+ doped samples show overlapping of Pr3+ excitation peak at 448 nm at the end of the broad excitation band of the host, indicating the charge transfer between the host and Pr3+ ions. Luminescence decay analysis confirmed concentration quenching in the prepared samples and the lifetime values are found to be in the microsecond range.

  11. Fracture resistance of monolithic zirconia molar crowns with reduced thickness.

    Science.gov (United States)

    Nakamura, Keisuke; Harada, Akio; Inagaki, Ryoichi; Kanno, Taro; Niwano, Yoshimi; Milleding, Percy; Örtengren, Ulf

    2015-01-01

    The purpose of the present study was to analyze the relationship between fracture load of monolithic zirconia crowns and axial/occlusal thickness and to evaluate the fracture resistance of monolithic zirconia crowns with reduced thickness in comparison with that of monolithic lithium disilicate crowns with regular thickness. Monolithic zirconia crowns (Lava Plus Zirconia, 3M/ESPE) with specified axial/occlusal thicknesses and lithium disilicate crowns (IPS e.max press, Ivoclar/Vivadent) with regular thickness were fabricated using a dental CAD/CAM system and a press technique, respectively. The crowns cemented onto dies were loaded until fracture. Based on measurements of the crown thickness made by micro-CT and the fracture load, multiple regression analysis was performed. It was revealed that the occlusal thickness significantly affected the fracture load (p zirconia crowns, the fracture load of the zirconia crowns with the occlusal thickness of 0.5 mm (5558 ± 522 N) was significantly higher than that of lithium disilicate crowns with an occlusal thickness of 1.5 mm (3147 ± 409 N). Within the limitations of the present study, it is suggested that monolithic zirconia crown with chamfer width of 0.5 mm and occlusal thickness of 0.5 mm can be used in the molar region in terms of fracture resistance.

  12. Synthesis and proton conducting properties of zirconia bridged hydrocarbon/phosphotungstic acid hybrid materials

    Energy Technology Data Exchange (ETDEWEB)

    Jedeok Kim; Honma, Itaru [National Institute of Advanced Science and Technology (AIST), Energy Electronics Inst., Tsukuba, Ibaraki (Japan)

    2004-08-15

    Recently, the organic/inorganic hybrid materials with flexibility, thermal, and chemical stabilities are extensively studied for the application of temperature tolerant polymer electrolyte fuel cells. This paper reports the preparation and properties of sol-gel derived proton conducting organic/inorganic materials based on zirconia bridged hydrocarbon phosphotungstic acids. The materials are molecular hybrids where linear hydrocarbons such as trimethylene glycols (TMGs) or octamethylene glycols (OMGs) are covalently bonded to zirconia interface to form macromolecular organic/inorganic networks. The hybrid materials become proton conducting polymer electrolytes by the addition of 12-phosphotungstic acids. The hybrid materials showed high thermal stability, and high protonic conductivity of 4 x 10{sup -3} S cm{sup -1} under saturated humidity condition at 150 deg C. The materials can be expected to be used for the application of temperature tolerant polymer electrolyte fuel cell. (Author)

  13. Synthesis and proton conducting properties of zirconia bridged hydrocarbon/phosphotungstic acid hybrid materials

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Je-Deok; Honma, Itaru

    2004-08-15

    Recently, the organic/inorganic hybrid materials with flexibility, thermal, and chemical stabilities are extensively studied for the application of temperature tolerant polymer electrolyte fuel cells. This paper reports the preparation and properties of sol-gel derived proton conducting organic/inorganic materials based on zirconia bridged hydrocarbon phosphotungstic acids. The materials are molecular hybrids where linear hydrocarbons such as trimethylene glycols (TMGs) or octamethylene glycols (OMGs) are covalently bonded to zirconia interface to form macromolecular organic/inorganic networks. The hybrid materials become proton conducting polymer electrolytes by the addition of 12-phosphotungstic acids. The hybrid materials showed high thermal stability, and high protonic conductivity of 4x10{sup -3} S cm{sup -1} under saturated humidity condition at 150 deg. C. The materials can be expected to be used for the application of temperature tolerant polymer electrolyte fuel cell.

  14. Phase characterization of precipitated zirconia

    International Nuclear Information System (INIS)

    Gutzov, S.; Ponahlo, J.; Lengauer, C.L.; Beran, A.

    1994-01-01

    The phase compositions of undoped and europium-doped zirconia samples, obtained by precipitation and thermal treatment from 350 to 1,000 C, have been investigated by powder X-ray diffractometry, infrared spectroscopy, and cathodoluminescence spectroscopy. The low-temperature stabilization of tetragonal zirconia is mainly controlled by the presence of anion additives, such as ammonium chloride. The influences of the crystallite size is less important. Cathodoluminescence spectra show a structural similarity between tetragonal and amorphous zirconia

  15. Fracture strength of monolithic and bi-layer zirconia-based crowns = : Resistência à fratura de coroas monolíticas e bicamada a base de zircônia

    OpenAIRE

    Deborah Pacheco Lameira

    2014-01-01

    Resumo: O objetivo deste estudo foi avaliar a resistência à fratura de coroas monolíticas e bicamada a base de zircônia, após envelhecimento artificial. Para este estudo, foram utilizados 32 incisivos bovinos onde foram feitos preparos de coroa total. Estes foram escaneados para a confecção de coroas a base de a zircônia tetragonal parcialmente estabilizada por ítrio (yttrium partially stabilized tetragonal zirconia polycrystalline Y-TZP), por um sistema CAD/CAM (computer-aided design and com...

  16. Zirconia as a Dental Biomaterial

    Directory of Open Access Journals (Sweden)

    Alvaro Della Bona

    2015-08-01

    Full Text Available Ceramics are very important in the science of dental biomaterials. Among all dental ceramics, zirconia is in evidence as a dental biomaterial and it is the material of choice in contemporary restorative dentistry. Zirconia has been applied as structural material for dental bridges, crowns, inserts, and implants, mostly because of its biocompatibility, high fracture toughness, and radiopacity. However, the clinical success of restorative dentistry has to consider the adhesion to different substrates, which has offered a great challenge to dental zirconia research and development. This study characterizes zirconia as a dental biomaterial, presenting the current consensus and challenges to its dental applications.

  17. Direct silanization of zirconia for increased biointegration.

    Science.gov (United States)

    Caravaca, Carlos; Shi, Liu; Balvay, Sandra; Rivory, Pascaline; Laurenceau, Emmanuelle; Chevolot, Yann; Hartmann, Daniel; Gremillard, Laurent; Chevalier, Jérôme

    2016-12-01

    High-performance bioinert ceramics such as zirconia have been used for biomedical devices since the early seventies. In order to promote osseointegration, the historical solution has been to increase the specific surface of the implant through roughness. Nevertheless these treatments on ceramics may create defects at the surface, exposing the material to higher chances of early failure. In zirconia, such treatments may also affect the stability of the surface. More recently, the interest of improving osseointegration of implants has moved the research focus towards the actual chemistry of the surface. Inspired by this, we have adapted the current knowledge and techniques of silica functionalization and applied it to successfully introduce 3-aminopropyldimethylethoxy silane (APDMES) directly on the surface of zirconia (3Y-TZP). We used plasma of oxygen to clean the surface and promote hydroxylation of the surface to increase silane density. The samples were extensively characterized by means of X-ray photoelectron spectroscopy (XPS) and contact angle, mechanically tested and its cytotoxicity was evaluated through cell adhesion and proliferation tests. Additionally, aging was studied to discard negative effects of the treatment on the stability of the tetragonal phase. No adverse effect was found on the mechanical response of treated samples. In addition, plasma-treated samples exhibited an unexpectedly higher resistance to aging. Finally, silane density was 35% lower than the one reported in literature for silica. However cells displayed a qualitatively higher spreading in opposition to the rounder appearance of cells on untreated zirconia. These results lay the foundations for the next generation of zirconia implants with biologically friendlier surfaces. The use of zirconia-based ceramics in biomedical devices is broad and well accepted, especially in dental implants. However, they do not bond naturally to bone, therefore to ensure fixation surgeons typically rely

  18. Development an efficient calibrated nonlocal plate model for nonlinear axial instability of zirconia nanosheets using molecular dynamics simulation.

    Science.gov (United States)

    Sahmani, S; Fattahi, A M

    2017-08-01

    New ceramic materials containing nanoscaled crystalline phases create a main object of scientific interest due to their attractive advantages such as biocompatibility. Zirconia as a transparent glass ceramic is one of the most useful binary oxides in a wide range of applications. In the present study, a new size-dependent plate model is constructed to predict the nonlinear axial instability characteristics of zirconia nanosheets under axial compressive load. To accomplish this end, the nonlocal continuum elasticity of Eringen is incorporated to a refined exponential shear deformation plate theory. A perturbation-based solving process is put to use to derive explicit expressions for nonlocal equilibrium paths of axial-loaded nanosheets. After that, some molecular dynamics (MD) simulations are performed for axial instability response of square zirconia nanosheets with different side lengths, the results of which are matched with those of the developed nonlocal plate model to capture the proper value of nonlocal parameter. It is demonstrated that the calibrated nonlocal plate model with nonlocal parameter equal to 0.37nm has a very good capability to predict the axial instability characteristics of zirconia nanosheets, the accuracy of which is comparable with that of MD simulation. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. A fast response oxygen sensor based upon a fully-sealed zirconia pump-gauge operated in the potentiometric mode

    Science.gov (United States)

    Benammar, M.; Maskell, W. C.

    1992-06-01

    An instrument for fast and continuous measurement of oxygen partial pressure not requiring a reference gas was constructed around a sealed zirconia oxygen pump-gauge sensor operated in the ac mode. By appropriate signal processing of the gauge EMF, the mean oxygen partial pressure within the sensor was determined and maintained constant via a feedback loop. Potentiometric measurement of the oxygen partial pressure in the sample gas was made relative to this controlled internal reference. The response time of the instrument for a step change in oxygen partial pressure from 1 to 10 kPa was only 65 ms. ned" OutputMedium="All"> 1 3 Proceedings of the 29th International Conference on the Applications of the Mössbauer Effect (ICAME 2007) held in Kanpur, India, 14-19 October 2007, PART IV/VII 30 2008 11 19 2008 11 18 2008 7 2008 Springer Science+Business Media B.V. 2008 9803 10.1007/s10751-008-9803-9 1 On the phenomena occurring at the interface between iron and iron–platinum thin films 1 7 2008 9 17 2008 10 10 Springer Science+Business Media B.V.

  20. Effect of Veneering Techniques on Shear and Microtensile Bond Strengths of Zirconia-Based All-Ceramic Systems.

    Science.gov (United States)

    Yilmaz Savas, Tuba; Aykent, Filiz

    2017-12-18

    To evaluate shear (SBS) and microtensile (μTBS) bond strengths of zirconia cores veneered using different fabrication techniques. Seventy-five IPS e.max ZirCAD plates were fabricated and divided into three groups according to the following veneering techniques: layering, pressing, and CAD-on. The specimens of the layering group were veneered with IPS e.max Ceram, and the specimens of the pressing group were veneered with IPS e.max Zir- Press. Veneering ceramics in the CAD-on group were milled from IPS e.max CAD, fused with the core by using a glass-fusion ceramic, and then crystallized. Bond strength tests were performed using a universal testing machine at a crosshead speed of 0.5 mm/min for the SBS test and 1 mm/min for the μTBS test. Mean SBS and μTBS (MPa) were analyzed with one-way ANOVA and Tukey's HSD test (p 0.05). The CAD-on technique showed the highest shear bond strengths of the tested groups, and most of the specimens failed cohesively instead of failing at the adhesive interface.

  1. Sintering additives for zirconia ceramics

    International Nuclear Information System (INIS)

    Wu, S.

    1986-01-01

    This book is an overview of sintering science and its application to zirconia materials including CaO, MgO, and Y/sub 2/O/sub 3/-CeO/sub 2/ doped materials. This book is a reference for first-time exposure to zirconia materials technology, particularly densification

  2. Sintering additives for zirconia ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, S.

    1986-01-01

    This book is an overview of sintering science and its application to zirconia materials including CaO, MgO, and Y/sub 2/O/sub 3/-CeO/sub 2/ doped materials. This book is a reference for first-time exposure to zirconia materials technology, particularly densification.

  3. The Novel Design of Zirconium Oxide-Based Screw-Retained Restorations, Maximizing Exposure of Zirconia to Soft Peri-implant Tissues: Clinical Report After 3 Years of Follow-up.

    Science.gov (United States)

    Linkevicius, Tomas

    Current use of zirconium oxide (ZrO₂)-based screw-retained restorations does not guarantee maximum contact of soft peri-implant tissues with ZrO₂, because veneering porcelain usually covers the major subgingival part of the restoration. Ceramics preclude direct interaction between zirconia and soft tissue cells, thus reducing biocompatibility and benefit to the patient. The four case reports discussed in this article describe the new design modality of the ZrO₂ screw-retained restorations, in which zirconia is exposed to the tissues and no veneering porcelain is located below the gingival margin. The article also shows the impact of this treatment on soft peri-implant tissues after 3 years of follow-up. Soft tissue recession, vestibular contour, bleeding on probing, and probing depth were evaluated.

  4. Biaxial flexural strength of bilayered zirconia using various veneering ceramics.

    Science.gov (United States)

    Chantranikul, Natravee; Salimee, Prarom

    2015-10-01

    The aim of this study was to evaluate the biaxial flexural strength (BFS) of one zirconia-based ceramic used with various veneering ceramics. Zirconia core material (Katana) and five veneering ceramics (Cerabien ZR; CZR, Lava Ceram; LV, Cercon Ceram Kiss; CC, IPS e.max Ceram; EM and VITA VM9; VT) were selected. Using the powder/liquid layering technique, bilayered disk specimens (diameter: 12.50 mm, thickness: 1.50 mm) were prepared to follow ISO standard 6872:2008 into five groups according to veneering ceramics as follows; Katana zirconia veneering with CZR (K/CZR), Katana zirconia veneering with LV (K/LV), Katana zirconia veneering with CC (K/CC), Katana zirconia veneering with EM (K/EM) and Katana zirconia veneering with VT (K/VT). After 20,000 thermocycling, load tests were conducted using a universal testing machine (Instron). The BFS were calculated and analyzed with one-way ANOVA and Tukey HSD (α=0.05). The Weibull analysis was performed for reliability of strength. The mode of fracture and fractured surface were observed by SEM. It showed that K/CC had significantly the highest BFS, followed by K/LV. BFS of K/CZR, K/EM and K/VT were not significantly different from each other, but were significantly lower than the other two groups. Weibull distribution reported the same trend of reliability as the BFS results. From the result of this study, the BFS of the bilayered zirconia/veneer composite did not only depend on the Young's modulus value of the materials. Further studies regarding interfacial strength and sintering factors are necessary to achieve the optimal strength.

  5. colorimetric evaluation of Cercon zirconia and metal ceramic restorations in two thicknesses of veneering porcelain

    Directory of Open Access Journals (Sweden)

    Dorriz H

    2011-02-01

    Full Text Available "nBackground and Aims: The aim of this study was to evaluate the effect of zirconia and base metal cores on the color of restorations. Furthermore, the effect of different backings on the color of cercon zirconia was evaluated."nMaterials and Methods: The specimens were Cercon zirconia and metal ceramic discs with "high Au" and "base metal" alloys. Cercon zirconia discs were veneered with veneering shade of A2 and two thickness of porcelain"n(0.7 mm, 1.2 mm. There were 3 discs in each group. Metal ceramic discs were made of "nickel-chromium" alloy (Verobond and "high Au" alloy (World 89 and two shades (A2, A3.5 and two thicknesses of veneering porcelain. 3 types of backing (high Au, nickel-chromium and A3 shade composite were made for Cercon zirconia discs. Spectrophotometric evaluation of zirconia discs (on 3 backings and metal ceramic discs was done. One-way ANOVA and Tukey tests were used for data analysis."nResults: There were no significant differences between the amounts of L*, a*, b* for Cercon zirconia on different backings (P>0.05. In comparison between different core groups, a* was significantly higher in metal ceramic groups compared with that of zirconia groups (P<0.05."nConclusion: Cercon zirconia can completely mask the underlying backing.

  6. Cladding oxidation model development based on diffusion equations and a simulation of the monoclinic-tetragonal phase transformation of zirconia during transient oxidation

    Science.gov (United States)

    He, Xiaoqiang; Yu, Hongxing; Jiang, Guangming; Dang, Gaojian; Wu, Dan; Zhang, Yu

    2014-08-01

    Zircaloy cladding oxidation is mostly represented by parabolic rate correlation. But the correlation approach is not suitable for long-term isothermal oxidation [4] or oxidation occurs under steam starvation conditions [5] and cannot obtain the detailed oxygen distribution which impacts the detailed mechanical behavior. To obtain the detailed oxygen distribution, a multi-phase diffusion problem with moving boundaries was introduced to simulate the cladding oxidation [9,10]. However, the hysteresis phenomenon related to the coexistence of monoclinic-tetragonal phases of zirconia which are very important to model the cladding oxidation during a LOCA, is not analyzed. In this study, a cladding oxidation model based on diffusion equations in the temperature range from 923 K to 2098 K which contains β-Zr, α-Zr, monoclinic-ZrO2, tetragonal-ZrO2, and cubic-ZrO2 is developed and the detailed oxygen distribution in the cladding could be obtained. It showed that the simulations of short-term and long-term isothermal oxidation, transient oxidation, and oxidation under steam starvation conditions were reasonable through comparing with the experimental data. We found that our model can give a reasonable simulation of the hysteresis phenomenon of monoclinic-tetragonal phase transformation during transient oxidation as well as a much better simulation of the hypothetical LOCA transient oxidation experiments [11] in ORNL than that by the code based on the parabolic rate correlation. This indicates that the developed model can accurately simulate the cladding oxidation during a LOCA transient.

  7. Wetting evaluation of silver based braze alloys onto zirconia metalized with reactive elements for application in oil well drill bots; Avaliacao do molhamento de ligas de adicao a base de prata sobre zirconia polida e metalizada com elementos ativos para aplicacao em brocas de perfuracao de pocos de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, J.C.; Silva, J.M.; Santos, P.R.F.; Nascimento, R.M.; Martinelli, A.E. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Dept. de Engenharia de Materiais], Email: jocabuzo@gmail.com; Pimenta, J.S. [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Dept. de Engenharia Mecanica

    2010-07-01

    Drill bits with hard ceramic inserts are often used on drilling operations. The cutting and crushing action of rocks will produce failures in the tricone bits, which are related to wear; total or partial rupture of the drill bit body or even the inserts; thermal shock and corrosion. The research of better drill bits with ceramic inserts thermally more stable and mechanically stronger, will lead to an increase of their lifetime, and so reducing costs of substitution and maintenance. In the present work, some silver based braze alloys were melted onto zirconia YSZ substrates metallized or not with active metals. inside a furnace with vacuum of 10{sup -5} mbar to evaluate the wetting behavior. The system with AgCuTi and the non metallized YSZ ceramic, showed low contact angles and stable interfaces, which may be appropriate for brazing metal/ceramic parts. (author)

  8. Evaluation of zirconia bonding to veneering porcelain

    OpenAIRE

    Aneta Mijoska; Mirjana Popovska

    2014-01-01

    Zirconium dioxide as core ceramic material for dental crowns and bridges, possess high strength, chemical stability and superior aesthetics after veneering. Veneering ceramic is considered to be the weakest part of all-ceramic restorations. The adhesion between the core and veneering porcelain is based on the manner in which the connection occurs in metal-ceramic structures. Standard procedures for connecting zirconia to hard dental tissues and veneering materials do not achieve the requir...

  9. Evaluation and comparison of the internal fit and marginal accuracy of base metal (nickelchromium) and zirconia copings before and after ceramic veneering: a sem study.

    Science.gov (United States)

    Regish, K M; Sharma, D; Prithviraj, D R; Nair, A; Raghavan, R

    2013-03-01

    This study compares the internal fit and marginal adaptation of copy milled Zirconia copings with Nickel-Chromium (Ni-Cr) copings fabricated using a lost wax technique before and after ceramic veneering. A standardized metal master die simulating a prepared crown was fabricated and twenty impressions of the metal die were made and poured with die stone. Wax patterns were made on ten dies and cast while light cure resin patterns were made on the other ten dies for copy milling the Zirconia copings. Five specimens from each group were subjected to ceramic veneering. All the test specimens were luted on to the fresh dies, embedded in dental plaster, sectioned and image analysis done using scanning electron microscopy. Thereafter statistical analysis is done using student t-test. The linear measurements for internal fit and marginal discrepancy were increased for Zirconia compared with Ni-Cr copings. The difference in the values of all the specimens of all the groups were not statistically significant (P > 0.05) except the values comparing the internal fit of Zirconia and Ni-Cr copings before ceramic veneering (P Zirconia copings but internal fit and marginal adaptability deteriorated after ceramic veneering.

  10. Hydrothermal crystallization of zirconia and zirconia solid solutions

    International Nuclear Information System (INIS)

    Pyda, W.; Haberko, K.; Bucko, M.M.

    1991-01-01

    Zirconia as well as yttria-zirconia and calcia-zirconia solid-solution powders were crystallized under hydrothermal conditions from (co)precipitated hydroxides. The morphology of the power particles is strongly dependent on the crystallization conditions. The powders crystallized in a water solution of Na, K, and Li hydroxides show elongated particles of much larger sizes than those which result from the process carried out in pure water or a water solution of Na, K, or Li chlorides. The shapes of the latter particles are isometric. In this paper the growth mechanism of the elongated particles is suggested

  11. EQCM Immunoassay for Phosphorylated Acetylcholinesterase as a Biomarker for Organophosphate Exposures Based on Selective Zirconia Adsorption and Enzyme-Catalytic Precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hua; Wang, Jun; Choi, Daiwon; Tang, Zhiwen; Wu, Hong; Lin, Yuehe

    2009-03-01

    A zirconia (ZrO2) adsorption-based immunoassay by electrochemical quartz crystal microbalance (EQCM) has been initially developed, aiming at the detection of phosphorylated acetylcholinesterase (AChE) as a potential biomarker for bio-monitoring exposures to organophosphate (OP) pesticides and chemical warfare agents. Hydroxyl-derivatized monolayer was preferably chosen to modify the crystal serving as the template for directing the electro-deposition of ZrO2 film with uniform nanostructures. The resulting ZrO2 film was utilized to selectively capture phosphorylated AChE from the sample media. Horseradish peroxidase (HRP)-labeled anti-AChE antibodies were further employed to recognize the captured phosphorylated protein. Enzyme-catalytic oxidation of the benzidine substrate resulted in the accumulation of insoluble product on the functionalized crystal. Ultrasensitive EQCM quantification by mass-amplified frequency responses as well as rapid qualification by visual color changes of product could be thus achieved. Moreover, 4-chloro-1-naphthol (CN) was comparably studied as an ideal chromogenic substrate for the enzyme-catalytic precipitation. Experimental results show that the developed EQCM technique can allow for the detection of phosphorylated AChE in human plasma. Such an EQCM immunosensing format opens a new door towards the development of simple, sensitive, and field-applicable biosensor for biologically monitoring low-level OP exposures.

  12. [PVD-silicoating before cementation of zirconia-based knee prostheses effects better cement adhesion and lower aseptic loosening rates].

    Science.gov (United States)

    Marx, R; Faramarzi, R; Oberbach, T; Begand, S; Grätz, N; Wirtz, D C

    2012-02-01

    CoCrMo alloys are contraindicated for allergy patients. For these patients, cemented or uncemented prostheses made of titanium alloy are indicated. Uncemented prostheses, however, have low primary retention, particularly the tibial components of knee joint prostheses because of the lack of a positive locking. Therefore, for knee replacement cemented CoCrMo prostheses may be suitable also for allergy sufferers if these are masked by ZrN or TiNbN layers. Alternatively the CoCrMo alloy may be replaced by high-strength oxide ceramics. For adhesion of bone cement to the ceramic surface, however, only inefficient mechanical retention spots are exposed as compared with a metal surface. Undercuts generated by corundum blasting, although highly efficient on a CoCrMo surface, are not such efficient centres on a ceramic surface due to its brittleness. Therefore, the mechanical component of retention is significantly reduced. When specific adhesion between bone cement and surface does not exist due to physical and chemical forces, the hydrolytic stability will be insufficient. Micromotions are promoted and early aseptic loosening is predictable. Silicoating of the ceramic surface will allow specific adhesion and can result in better hydrolytic stability of bonding. In order to evaluate the effectiveness of silicoating the bond strengths of blasted (mean size of corundum grains 50 µm) and silicate layered alumina-toughened zirconia (ATZ) surfaces were compared with "as fired" surfaces by utilising TiAlV probes (diameter 6 mm) for traction-adhesive strength testing. Samples machined out of CoCrMo alloy were utilised for reference. After preparing the samples for traction-adhesive strength testing (sequence: substrate, silicate and silane, protective lacquer [PolyMA], bone cement, TiAlV probe) they were aged up to 360 days at 37 °C in Ringer's solution. The bond strengths observed for all ageing intervals were well above 20 MPa and much higher and more hydrolytically

  13. Evaluation of bond strength of various margin ceramics to a zirconia ceramic

    NARCIS (Netherlands)

    Comlekoglu, M. Erhan; Dundar, Mine; Ozcan, Mutlu; Gungor, M. Ali; Gokce, Bulent; Artunc, Celal

    2008-01-01

    Objective: This study evaluated the bond strengths of four different margin ceramics based on fluoroapatite and feldspath to a zirconia ceramic. Methods: Zirconia cores (Zirconzahn) (N = 28, n = 7/margin ceramic group) were fabricated according to the manufacturers' instructions (diameter: 4 mm;

  14. Fracture performance of computer-aided manufactured zirconia and alloy crowns

    NARCIS (Netherlands)

    Rosentritt, M.; Behr, M.; Thaller, C.; Rudolph, H.; Feilzer, A.J.

    2009-01-01

    Objective: To compare the fracture resistance and fracture performance of CAD/CAM zirconia and alloy crowns. Method and Materials: One electrophoretic deposition alumina ceramic (Wolceram, Wolceram) and 4 zirconia-based systems (ce.novation, ce.novation; Cercon, DeguDent; Digizon, Amann Girrbach;

  15. Effect of amine counterion type on the retention of basic compounds on octadecyl silane bonded silica-based and polybutadiene-coated zirconia phases.

    Science.gov (United States)

    Yang, Xiqin; Dai, Jun; Carr, Peter W

    2003-07-01

    In a previous paper, we compared the mixed-mode retention characteristics of cationic solutes on octadecyl silane-bonded silica (ODS) and polybutadiene-coated zirconia (PBD-ZrO2) phases. It is well recognized that both reversed-phase and ion-exchange interactions contribute to the retention of cations on ODS phases. The reversed-phase interaction results from the bonded hydrocarbon chain; the ion-exchange interaction originates in the ionized residual silanol groups. These two types of interactions also exist on the PBD-ZrO2 phase. The polybutadiene contributes to the reversed-phase interaction and the ionized zirconol, but primarily, the adsorbed Lewis base anions, such as phosphate or fluoride, contribute to the ion-exchange interaction. We have shown that on ODS phases, reversed-phase interactions are much more important, whereas the opposite is true of PBD-ZrO2 phases. In this work, we investigate the effect of several amine mobile phase counterions on the retention of cationic solutes on ODS and PBD-ZrO2 phases. The effects of the chain length and the type of amine (1 degree, 2 degrees, 3 degrees) counterion on the retention of basic compounds were studied. In contrast to older studies of type A silica-based phases, the results show that the chain length and type of the amine blocker do not have a large effect on the retention of basic compounds with the newer type B silica-based materials. However, on the PBD-ZrO2 phase, very striking differences in retention were observed with different amine counterions. We show that the molecular geometry of the amine counterion has a significant effect on the retention of basic solutes on the PBD-ZrO2 phase.

  16. Evaluation of zirconia bonding to veneering porcelain

    Directory of Open Access Journals (Sweden)

    Aneta Mijoska

    2014-10-01

    Full Text Available Zirconium dioxide as core ceramic material for dental crowns and bridges, possess high strength, chemical stability and superior aesthetics after veneering. Veneering ceramic is considered to be the weakest part of all-ceramic restorations. The adhesion between the core and veneering porcelain is based on the manner in which the connection occurs in metal-ceramic structures. Standard procedures for connecting zirconia to hard dental tissues and veneering materials do not achieve the required strength of bonding. The aim of the paper is to investigate different surface treatments of the zirconium dioxide ceramic core and find the best, for achieving highest adhesive bonding values to veneering porcelain. The study was primarily designed to investigate the bonding strength of the veneering porcelain to zirconia with in vitro Macro shear bond strength test. The specimens with different surface treatment of the zirconia were divided in five groups of twelve according to the treatment of zirconium surface and results showed highest bonding values for specimens treated with Rocatec system.

  17. Zirconia as a Dental Biomaterial

    OpenAIRE

    Alvaro Della Bona; Oscar E. Pecho; Rodrigo Alessandretti

    2015-01-01

    Ceramics are very important in the science of dental biomaterials. Among all dental ceramics, zirconia is in evidence as a dental biomaterial and it is the material of choice in contemporary restorative dentistry. Zirconia has been applied as structural material for dental bridges, crowns, inserts, and implants, mostly because of its biocompatibility, high fracture toughness, and radiopacity. However, the clinical success of restorative dentistry has to consider the adhesion to different subs...

  18. Influence of surface modification techniques on shear bond strength between different zirconia cores and veneering ceramics

    Science.gov (United States)

    Rismanchian, Mansour; Savabi, Omid; Ashtiani, Alireza Hashemi

    2011-01-01

    PURPOSE Veneering porcelain might be delaminated from underlying zirconia-based ceramics. The aim of this study was the evaluation of the effect of different surface treatments and type of zirconia (white or colored) on shear bond strength (SBS) of zirconia core and its veneering porcelain. MATERIALS AND METHODS Eighty zirconia disks (40 white and 40 colored; 10 mm in diameter and 4 mm thick) were treated with three different mechanical surface conditioning methods (Sandblasting with 110 µm Al2O3 particle, grinding, sandblasting and liner application). One group had received no treatment. These disks were veneered with 3 mm thick and 5 mm diameter Cercon Ceram Kiss porcelain and SBS test was conducted (cross-head speed = 1 mm/min). Two and one way ANOVA, Tukey's HSD Past hoc, and T-test were selected to analyzed the data (α=0.05). RESULTS In this study, the factor of different types of zirconia ceramics (P=.462) had no significant effect on SBS, but the factors of different surface modification techniques (P=.005) and interaction effect (P=.018) had a significant effect on SBS. Within colored zirconia group, there were no significant differences in mean SBS among the four surface treatment subgroups (P=0.183). Within white zirconia group, "Ground group" exhibited a significantly lower SBS value than "as milled" or control (P=0.001) and liner (P=.05) groups. CONCLUSION Type of zirconia did not have any effect on bond strength between zirconia core and veneer ceramic. Surface treatment had different effects on the SBS of the different zirconia types and grinding dramatically decreased the SBS of white zirconia-porcelain. PMID:22259706

  19. Stock Versus CAD/CAM Customized Zirconia Implant Abutments - Clinical and Patient-Based Outcomes in a Randomized Controlled Clinical Trial

    NARCIS (Netherlands)

    Schepke, Ulf; Meijer, Henny J. A.; Kerdijk, Wouter; Raghoebar, Gerry M.; Cune, Marco

    BackgroundSingle-tooth replacement often requires a prefabricated dental implant and a customized crown. The benefits of individualization of the abutment remain unclear. PurposeThis randomized controlled clinical trial aims to study potential benefits of individualization of zirconia implant

  20. Effects of Hot Chemical Etching and 10-Metacryloxydecyl Dihydrogen Phosphate (MDP) Monomer on the Bond Strength of Zirconia Ceramics to Resin-Based Cements.

    Science.gov (United States)

    Akay, Canan; Çakırbay Tanış, Merve; Şen, Murat

    2017-07-01

    The purpose of this in vitro study was to evaluate the hot chemical etching method on the shear bond strength between zirconia and two resin cements. Sixty zirconia specimens (13 × 7.5 × 2.5 mm 3 ) were prepared and treated as follows: (1) airborne-particle abrasion with 50 μm Al 2 O 3 particles; (2) hot chemical etching for 10 minutes; (3) hot chemical etching for 30 minutes. Sixty composite cylinders of 3 mm diameter and height were prepared and bonded to zirconia specimens, which were divided into subgroups A and B. Group A: cemented with conventional resin cement (Variolink II); group B: cemented with 10-metacryloxydecyl dihydrogen phosphate (MDP) monomer containing resin cement (Panavia SA) after the application of surface treatments. Next, the specimens were stored in 37ºC distilled water for 24 hours. Following water storage, shear bond strength test was performed at a 1 mm/min crosshead speed in a universal testing machine. The statistical analyses were performed with one-way ANOVA and post hoc Tukey tests. p MDP monomer-containing resin cement, Panavia SA, improved the resin bonding of zirconia ceramics when combined with airborne-particle abrasion. © 2016 by the American College of Prosthodontists.

  1. Using zirconia-based prosthesis in a complete-mouth reconstruction treatment for worn dentition with the altered vertical dimension of occlusion.

    Science.gov (United States)

    Nam, Jung; Tokutomi, Hiro

    2015-02-01

    This clinical report describes the complete mouth reconstruction of a patient with a worn dentition. Computer-aided design and computer-aided manufacturing processed porcelain fused-to-zirconia prostheses were used to achieve good esthetics, function, and biomechanics. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  2. Comparison of Marginal Fit in Zirconia-Based All-Ceramic Frameworks (Cercon Made by Two Approaches (Direct and Wax-Up Scanning

    Directory of Open Access Journals (Sweden)

    Somayeh Zeighami

    2012-02-01

    Full Text Available Background and Aims: Since a large marginal opening allows more plaque accumulation, gingival sulcular fluid flow and bone loss, microleakage, recurrent caries and periodontal disease, marginal fit is of great importance in fixed restorations. The aim of this study was to compare the marginal fit of zirconium-based all ceramic (Cercon frameworks, made by two different approaches (Direct and Wax-up scanning.Materials and Methods: An abutment analog, with 5.5 mm width and height, was selected as an experimental model. Twenty all ceramic cores were made for this model (10 specimens per each group. In the first group (Direct, experimental models were scanned directly using Computer Aided Design/Computer Aided Manufacturing (CAD/CAM. The core was then designed with the aid of a computer and machined. In the second group (Wax-up or CAM a wax-up pattern was made on the experimental model and then scanned and milled from Cercon blocks. The marginal discrepancy of each specimen was recorded using a stereomicroscope (SZX9, Olympus, Japan and digital camera (Mode TK, C1380E, JVC, Japan and then measured by Adobe Photoshop CS software. The data were analyzed using T-test.Results: Mean marginal discrepancy of Direct group (85.2±3.95 µm was significantly less than that of Wax-up group (120.2±6.91 µm.Conclusion: Improved marginal fit of zirconia ceramics was found with the direct model scanning compared with that of Wax-up scanning using CAD/CAM.

  3. Osseointegration of zirconia implants compared with titanium: an in vivo study

    Science.gov (United States)

    Depprich, Rita; Zipprich, Holger; Ommerborn, Michelle; Naujoks, Christian; Wiesmann, Hans-Peter; Kiattavorncharoen, Sirichai; Lauer, Hans-Christoph; Meyer, Ulrich; Kübler, Norbert R; Handschel, Jörg

    2008-01-01

    Background Titanium and titanium alloys are widely used for fabrication of dental implants. Since the material composition and the surface topography of a biomaterial play a fundamental role in osseointegration, various chemical and physical surface modifications have been developed to improve osseous healing. Zirconia-based implants were introduced into dental implantology as an altenative to titanium implants. Zirconia seems to be a suitable implant material because of its tooth-like colour, its mechanical properties and its biocompatibility. As the osseointegration of zirconia implants has not been extensively investigated, the aim of this study was to compare the osseous healing of zirconia implants with titanium implants which have a roughened surface but otherwise similar implant geometries. Methods Forty-eight zirconia and titanium implants were introduced into the tibia of 12 minipigs. After 1, 4 or 12 weeks, animals were sacrificed and specimens containing the implants were examined in terms of histological and ultrastructural techniques. Results Histological results showed direct bone contact on the zirconia and titanium surfaces. Bone implant contact as measured by histomorphometry was slightly better on titanium than on zirconia surfaces. However, a statistically significant difference between the two groups was not observed. Conclusion The results demonstrated that zirconia implants with modified surfaces result in an osseointegration which is comparable with that of titanium implants. PMID:19077228

  4. Influence of Surface Treatments on the Bond Strength of Resin Cements to Monolithic Zirconia.

    Science.gov (United States)

    Elsaka, Shaymaa E

    To assess the influence of surface treatment on the microtensile bond strength (μTBS) of resin cements to monolithic zirconia materials. Two types of monolithic zirconia (Zenostar T [ZT] and Prettau Anterior [PA]) were evaluated. The specimens were assigned to three groups based on the surface treatment applied: group 1: control, assintered; group 2: sandblasted with 50-μm Al₂O₃; group 3: tribochemically silica sandblasted. Two types of resin cements (Multilink Speed [MS] and Multilink N [MN]) were applied to each group for evaluating the bond strength using the μTBS test. The fractured specimens were observed with a stereomicroscope and SEM. Surface roughness and topography of monolithic zirconia were examined after treatment. Data were analyzed using ANOVA and Tukey's test. A Weibull analysis was performed on the bond strength data. The bond strength was significantly affected by the surface treatment and the type of resin cement (p zirconia (p = 0.387). Surface treatment with tribochemical silica sandblasting revealed significantly higher bond strength (p zirconia was changed due to surface treatments. The surface treatment of monolithic zirconia with tribochemical silica sandblasting enhanced the bond strength between zirconia and resin cements. Resins cements containing adhesive phosphate monomer (APM, MS) provided higher bond strength to monolithic zirconia than non-APM (MN).

  5. Corrosion behavior of zirconia in acidulated phosphate fluoride

    Directory of Open Access Journals (Sweden)

    Anie Thomas

    2016-02-01

    Full Text Available ABSTRACT Objective The corrosion behavior of zirconia in acidulated phosphate fluoride (APF representing acidic environments and fluoride treatments was studied. Material and Methods Zirconia rods were immersed in 1.23% and 0.123% APF solutions and maintained at 37°C for determined periods of time. Surfaces of all specimens were imaged using digital microscopy and scanning electron microscopy (SEM. Sample mass and dimensions were measured for mass loss determination. Samples were characterized by powder X-ray diffraction (XRD to detect changes in crystallinity. A biosensor based on electrochemical impedance spectroscopy (EIS was used to detect ion dissolution of material into the immersion media. Results Digital microscopy revealed diminishing luster of the materials and SEM showed increased superficial corrosion of zirconia submerged in 1.23% APF. Although no structural change was found, the absorption of salts (sodium phosphate onto the surface of the materials bathed in 0.123% APF was significant. EIS indicated a greater change of impedance for the immersion solutions with increasing bathing time. Conclusion Immersion of zirconia in APF solutions showed deterioration limited to the surface, not extending to the bulk of the material. Inferences on zirconia performance in acidic oral environment can be elucidated from the study.

  6. Corrosion behavior of zirconia in acidulated phosphate fluoride

    Science.gov (United States)

    Thomas, Anie; Sridhar, Sathyanarayanan; Aghyarian, Shant; Watkins-curry, Pilanda; Chan, Julia Y.; Pozzi, Alessandro; Rodrigues, Danieli C.

    2016-01-01

    ABSTRACT Objective The corrosion behavior of zirconia in acidulated phosphate fluoride (APF) representing acidic environments and fluoride treatments was studied. Material and Methods Zirconia rods were immersed in 1.23% and 0.123% APF solutions and maintained at 37°C for determined periods of time. Surfaces of all specimens were imaged using digital microscopy and scanning electron microscopy (SEM). Sample mass and dimensions were measured for mass loss determination. Samples were characterized by powder X-ray diffraction (XRD) to detect changes in crystallinity. A biosensor based on electrochemical impedance spectroscopy (EIS) was used to detect ion dissolution of material into the immersion media. Results Digital microscopy revealed diminishing luster of the materials and SEM showed increased superficial corrosion of zirconia submerged in 1.23% APF. Although no structural change was found, the absorption of salts (sodium phosphate) onto the surface of the materials bathed in 0.123% APF was significant. EIS indicated a greater change of impedance for the immersion solutions with increasing bathing time. Conclusion Immersion of zirconia in APF solutions showed deterioration limited to the surface, not extending to the bulk of the material. Inferences on zirconia performance in acidic oral environment can be elucidated from the study. PMID:27008257

  7. Shear bond strength of veneering porcelain to porous zirconia.

    Science.gov (United States)

    Nakamura, Takashi; Sugano, Tsuyoshi; Usami, Hirofumi; Wakabayashi, Kazumichi; Ohnishi, Hiroshi; Sekino, Tohru; Yatani, Hirofumi

    2014-01-01

    In this study, two types of porous zirconia and dense zirconia were used. The flexural strength of non-layered zirconia specimens and those of the layered zirconia specimens with veneering porcelain were examined. Furthermore, the shear bond strength of veneering porcelain to zirconia was examined. The flexural strength of the non-layered specimens was 1,220 MPa for dense zirconia and 220 to 306 MPa for porous zirconia. The flexural strength of the layered specimens was 360 MPa for dense zirconia and 132 to 156 MPa for porous zirconia, when a load was applied to the porcelain side. The shear bond strength of porcelain veneered to dense zirconia was 27.4 MPa and that of porcelain veneered to porous zirconia was 33.6 to 35.1 MPa. This suggests that the veneering porcelain bonded strongly to porous zirconia although porous zirconia has a lower flexural strength than dense zirconia.

  8. Zirconia-TZP and alumina--advanced technologies for the manufacturing of single crowns.

    Science.gov (United States)

    Luthardt, R G; Sandkuhl, O; Reitz, B

    1999-12-01

    All-ceramic crowns based on Zirconia-TZP-frameworks should have advantages in comparison to copings of Alumina (PROCERA-AllCeram) because of their mechanical properties. Zirconia-TZP-frameworks were manufactured after optical digitising using a modified Precident-DCS-System. The mean fracture strength and the vertical marginal discrepancy of Zirconia-TZP-frameworks and Alumina-copings (PROCERA-AllCeram) were determined. Additionally the bonding strength of suitable veneering ceramics on pre-treated Zirconia-TZP surfaces was examined using the scratch test and the shear bonding strength. The results show that the bonding between Zirconia-TZP and the veneering ceramics as well as the precision of fit of the veneered crowns are comparable with established systems.

  9. Resin adhesion strengths to zirconia ceramics after primer treatment with silane coupling monomer or oligomer.

    Science.gov (United States)

    Okada, Masahiro; Inoue, Kazusa; Irie, Masao; Taketa, Hiroaki; Torii, Yasuhiro; Matsumoto, Takuya

    2017-09-26

    Resin bonding to zirconia ceramics is difficult to achieve using the standard methods for conventional silica-based dental ceramics, which employ silane coupling monomers as primers. The hypothesis in this study was that a silane coupling oligomer -a condensed product of silane coupling monomers- would be a more suitable primer for zirconia. To prove this hypothesis, the shear bond strengths between a composite resin and zirconia were compared after applying either a silane coupling monomer or oligomer. The shear bond strength increased after applying a non-activated ethanol solution of the silane coupling oligomer compared with that achieved when applying the monomer. Thermal treatment of the zirconia at 110°C after application of the silane coupling agents was essential to improve the shear bond strength between the composite resin cement and zirconia.

  10. Effects of temperature-gradient-induced damage of zirconia metering nozzles

    Science.gov (United States)

    Zhao, Liang; Xue, Qun-hu

    2017-09-01

    The effects of temperature-gradient-induced damage of zirconia metering nozzles were investigated through analysis of the phase composition and microstructure of nozzle samples. The analysis was carried out using X-ray diffraction and scanning electron microscopy after the samples were subjected to a heat treatment based on the temperatures of the affected, transition, and original layers of zirconia metering nozzles during the continuous casting of steel. The results showed that, after heat treatment at 1540, 1410, or 1300°C for a dwell time of 5 h, the monoclinic zirconia phase was gradually stabilized with increasing heat-treatment temperature. Moreover, a transformation to the cubic zirconia phase occurred, accompanied by grain growth, which illustrates that the temperature gradient in zirconia metering nozzles affects the mineral composition and microstructure of the nozzles and accelerates damage, thereby deteriorating the quality and service life of the nozzles.

  11. Synthesis of Pharmacological Heterocyclic Derivatives Based Surfactants.

    Science.gov (United States)

    El-Sayed, Refat; Fadda, Ahmed A

    2016-01-01

    Synthesis of chromenopyrimidine derivatives and the related fused system carried out by the reaction of chromene derivative 1 with various reagents under suitable reaction conditions. Condensation of stearoyl chloride with these heterocycles, then, propoxylated the products using propylene oxide to produce surface active agents having a twofold capacity as surface and antimicrobial dynamic specialists which may be served in the production of medications, pesticides, beautifying agents or may be utilized as an antimicrobial. Some of the surface properties and antimicrobial activity were resolved.

  12. Pro-inflammatory cytokines at zirconia implants and teeth. A cross-sectional assessment

    OpenAIRE

    Cionca, Norbert; Hashim, Dena Talal; Cancela, José Antonio; Giannopoulou, Catherine; Mombelli, Andrea

    2016-01-01

    OBJECTIVES: The aim of this study was to compare the expression of host-derived markers in peri-implant/gingival crevicular fluid (PCF/GCF) and clinical conditions at ceramic implants and contralateral natural teeth. As a secondary objective, we compared zirconia implants with titanium implants. METHODS: One zirconia implant (ZERAMEX(R) Implant System) and one contralateral natural tooth were examined in 36 systemically healthy subjects (21 males, 15 females, mean age 58). The levels of Il-1b...

  13. Evaluation of participants' perception and taste thresholds with a zirconia palatal plate.

    Science.gov (United States)

    Wada, Takeshi; Takano, Tomofumi; Tasaka, Akinori; Ueda, Takayuki; Sakurai, Kaoru

    2016-10-01

    Zirconia and cobalt-chromium can withstand a similar degree of loading. Therefore, using a zirconia base for removable dentures could allow the thickness of the palatal area to be reduced similarly to metal base dentures. We hypothesized that zirconia palatal plate for removable dentures provides a high level of participants' perception without influencing taste thresholds. The purpose of this study was to evaluate the participants' perception and taste thresholds of zirconia palatal plate. Palatal plates fabricated using acrylic resin, zirconia, and cobalt-chromium alloy were inserted into healthy individuals. Taste thresholds were investigated using the whole-mouth gustatory test, and participants' perception was evaluated using the 100-mm visual analog scale to assess the ease of pronunciation, ease of swallowing, sensation of temperature, metallic taste, sensation of foreign body, subjective sensory about weight, adhesiveness of chewing gum, and general satisfaction. For the taste thresholds, no significant differences were noted in sweet, salty, sour, bitter, or umami tastes among participants wearing no plate, or the resin, zirconia, and metal plates. Speech was easier and foreign body sensation was lower with the zirconia plate than with the resin plate. Evaluation of the adhesiveness of chewing gum showed that chewing gum does not readily adhere to the zirconia plate in comparison with the metal plate. The comprehensive participants' perception of the zirconia plate was evaluated as being superior to the resin plate. A zirconia palatal plate provides a high level of participants' perception without influencing taste thresholds. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  14. Evaluation of resin adhesion to zirconia ceramic using some organosilanes

    NARCIS (Netherlands)

    Matinlinna, Jukka P.; Heikkinen, Mo; Ozcan, Mutlu; Lassila, Lippo V. J.; Vallittu, Pekka K.

    Objectives. This study evaluated and compared the effect of three trialkoxysilane coupling agents on the bond strength of a Bis-GMA-based unfilled resin and a dimethacrylate-based resin composite luting cement to a zirconia ceramics (Procera(R) AllZircon, Nobel Biocare, Goteborg, Sweden). Methods.

  15. Phase composition of yttrium-doped zirconia ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Hennig, Christoph; Scheinost, Andreas C. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Molecular Structures; Weiss, Stephan [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes; Ikeda-Ohno, Atsushi [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Chemistry of the F-Elements; Gumeniuk, R. [Technische Univ. Bergakademie Freiberg (Germany). Inst. fuer Experimentelle Physik

    2017-06-01

    Ceramic material might be an alternative to borosilicate glass for the immobilization of nuclear waste. The crystallinity of ceramic material increases the corrosion resistance over several magnitudes in relation to amorphous glasses. The stability of such ceramics depend on several parameters, among them the crystal phase composition. A reliable quantitative phase analysis is necessary to correlate the macroscopic material properties with structure parameters. We performed a feasibility study based on yttrium-doped zirconia ceramics as analogue for trivalent actinides to ascertain that the nanosized crystal phases in zirconia ceramics can be reliably determined.

  16. Biaxial flexural strength of bilayered zirconia using various veneering ceramics

    OpenAIRE

    Chantranikul, Natravee; Salimee, Prarom

    2015-01-01

    PURPOSE The aim of this study was to evaluate the biaxial flexural strength (BFS) of one zirconia-based ceramic used with various veneering ceramics. MATERIALS AND METHODS Zirconia core material (Katana) and five veneering ceramics (Cerabien ZR; CZR, Lava Ceram; LV, Cercon Ceram Kiss; CC, IPS e.max Ceram; EM and VITA VM9; VT) were selected. Using the powder/liquid layering technique, bilayered disk specimens (diameter: 12.50 mm, thickness: 1.50 mm) were prepared to follow ISO standard 6872:20...

  17. Effect of zirconia-modified magnesia investment on the casting of pure titanium.

    Science.gov (United States)

    Hung, Chun-Cheng; Hou, Guey-Lin; Tsai, Chi-Cheng; Huang, Ching-Cheng

    2003-03-01

    Several investigations have examined magnesia-based investments for pure titanium casting. However, the thermal expansion value was insufficient at low casting temperatures and high interfacial reactivity occurred at high casting temperatures. The purpose of this investigation was to modify a magnesia-based investment by adding a heat-resistant mold material, zirconia, in different ratios to produce a more accurate titanium casting. The thermal expansion value was measured using a new precise automatic laser recording machine and pure titanium was cast using an argon casting machine. The marginal accuracy was measured using a stereomicroscope and the interfacial reactivity of the titanium was evaluated using X-ray diffraction analysis. The results indicate that adding different amounts of zirconia to a magnesia-based investment can increase its thermal expansion value and decrease the interfacial reactivity of the titanium. Maximal thermal expansion in the zirconia-modified investments significantly increased by 5-6 weight % (wt%) and peaked at 1.62% expansion. Selevest with 5 wt% zirconia had the smallest mean marginal discrepancy, 21.70 microm at 750 degrees C. Analysis of variance indicates significant differences in marginal discrepancy between zirconia-modified investments (p zirconia can also decrease the interfacial reactivity of the titanium. The data indicated that proper amounts of zirconia (5-6 wt%) added to a magnesia-based investment can produce a more accurate and less interfacial reactive pure titanium casting.

  18. Development of a nano structured system based on zirconia and Co nanoparticles for thermoluminescent applications: sensor of gamma and UV radiation

    International Nuclear Information System (INIS)

    Villa S, G.

    2014-01-01

    Powders of zirconium IV oxide as well as systems composed of zirconia nano crystals and cobalt nanoparticles (ZrO 2 :NPCo) with dimensions of nanometers were synthesized by the sol-gel method. Zirconia and ZrO 2 :NPCo systems have crystalline structure tetragonal or monoclinic is the heat treatment was to 500 and 1000 degrees Celsius respectively. The characterization of the synthesized materials consisted of a morphological and structural analysis, the information obtained was correlated to its thermoluminescent response induced by gamma and ultraviolet radiation. Thermoluminescent behavior was analyzed on different concentrations of cobalt nanoparticles incorporated during the synthesis process of the zirconium oxide. The monoclinic structure has the highest sensitivity thermoluminescent induced by ultraviolet and gamma radiation. Moreover, the thermoluminescence intensity decreased considerably in ZrO 2 :NPCo systems and was induced the growth of a glow peak at 280 degrees Celsius. In most of the materials analyzed the relation of the thermoluminescence intensity depending the time of irradiation with ultraviolet light showed the saturation of the traps in the material after 60 s of irradiation. Using gamma radiation is observed a behavior linear in the applied dose range between 0.25 Gy and 450 Gy. The growth of a glow peak at 280 degrees Celsius is the most important change in the thermoluminescence characteristics of zirconia. The ZrO 2 :NPCo systems can be used in the development of thermoluminescent dosimeters for detecting gamma radiation fields mainly. (Author)

  19. Ceramic wear maps: Zirconia

    International Nuclear Information System (INIS)

    Lee, S.W.; Hsu, S.M.; Shen, M.C.

    1993-01-01

    The wear characteristics of an yttria-stabilized zirconia (Y-TZP) are represented by a set of three-dimensional wear maps under dry and lubricated conditions. Water, paraffin oil, and a formulated oil were used as lubricants. Different wear regions were identified as a function of load, speed, and lubrication environment. Sudden increases in wear, identified as ear transitions, were found at certain loads and speeds. The onset of wear transitions was moderated by the presence of a lubricant. Below the wear transitions, the wear was mild and the wear mechanism was predominantly plastic deformation and microfracture. Above the wear transitions, the wear was severe, dominated by brittle fracture and third-body abrasion. Different fluids had different effects on wear. Water had a deleterious effect on wear for this material. The presence of oil lubricants effectively reduced friction and moderated wear. Under high load and high speed, additional stress induced by a thermal gradient within a small area contributed significantly to wear. A critical velocity model was found to describe the locations of the wear transition zones successfully

  20. Martensitic transformation in zirconia

    International Nuclear Information System (INIS)

    Deville, Sylvain; Guenin, Gerard; Chevalier, Jerome

    2004-01-01

    We investigate by atomic force microscopy (AFM) the surface relief resulting from martensitic tetragonal to monoclinic phase transformation induced by low temperature autoclave aging in ceria-stabilized zirconia. AFM appears as a very powerful tool to investigate martensite relief quantitatively and with a great precision. The crystallographic phenomenological theory is used to predict the expected relief induced by the transformation, for the particular case of lattice correspondence ABC1, where tetragonal c axis becomes the monoclinic c axis. A model for variants spatial arrangement for this lattice correspondence is proposed and validated by the experimental observations. An excellent agreement is found between the quantitative calculations outputs and the experimental measurements at nanometer scale yielded by AFM. All the observed features are explained fully quantitatively by the calculations, with discrepancies between calculations and quantitative experimental measurements within the measurements and calculations precision range. In particular, the crystallographic orientation of the transformed grains is determined from the local characteristics of transformation induced relief. It is finally demonstrated that the strain energy is the controlling factor of the surface transformation induced by low temperature autoclave treatments in this material

  1. Photocatalytic Based Degradation Processes of Lignin Derivatives

    Directory of Open Access Journals (Sweden)

    Colin Awungacha Lekelefac

    2015-01-01

    Full Text Available Photocatalysis, belonging to the advanced oxidation processes (AOPs, is a potential new transformation technology for lignin derivatives to value added products (e.g., phenol, benzene, toluene, and xylene. Moreover, lignin represents the only viable source to produce aromatic compounds as fossil fuel alternative. This review covers recent advancement made in the photochemical transformation of industrial lignins. It starts with the photochemical reaction principle followed by results obtained by varying process parameters. In this context, influences of photocatalysts, metal ions, additives, lignin concentration, and illumination intensity and the influence of pH are presented and discussed. Furthermore, an overview is given on several used process analytical methods describing the results obtained from the degradation of lignin derivatives. Finally, a promising concept by coupling photocatalysis with a consecutive biocatalytic process was briefly reviewed.

  2. Bond strength of a resin cement to high-alumina and zirconia-reinforced ceramics: The effect of surface conditioning

    NARCIS (Netherlands)

    Valandro, L.F.; Ozcan, M.; Bottino, M.C.; Bottino, M.A.; Scotti, R.; Della Bona, A.

    2006-01-01

    Purpose: The aim of this study was to evaluate the effect of two surface conditioning methods on the microtensile bond strength of a resin cement to three high-strength core ceramics: high alumina-based (In-Ceram Alumina, Procera AllCeram) and zirconia-reinforced alumina-based (in-Ceram Zirconia)

  3. Bond strength of a resin cement to high-alumina and zirconia-reinforced ceramics : The effect of surface conditioning

    NARCIS (Netherlands)

    Felipe Valandro, Luiz; Ozcan, Mutlu; Bottino, Marco Cicero; Bottino, Marco Antonio; Scotti, Roberto; Della Bona, Alvaro

    Purpose: The aim of this study was to evaluate the effect of two surface conditioning methods on the microtensile bond strength of a resin cement to three high-strength core ceramics: high alumina-based (In-Ceram Alumina, Procera AllCeram) and zirconia-reinforced alumina-based (in-Ceram Zirconia)

  4. Microstructural aspects of zirconia thermal barrier coatings

    Science.gov (United States)

    Mitchell, T. E.; Suhr, D. S.; Keller, R. J.; Lanteri, V.; Heuer, A. H.

    1985-01-01

    Various combination of plasma-sprayed bond coatings and zirconia ceramic coatings on a nickel-based superalloy substrate were tested by static thermal exposure at 1200 C and cyclic thermal exposure to 1000 C. The bond coats were based on Ni-Cr-Al alloys with additions of rare earth elements and Si. The ceramic coats were various ZrO2-Y2O3 compositions, of which the optimum was found to be ZrO2-8.9 wt percent Y2O3. Microstructural analysis showed that resistance to cracking during thermal exposure is strongly related to deleterious phase changes. Zones depleted of Al formed at the bond coat/ceramic coat interface due to oxidation and at the bond coat/substrate interface due to interdiffusion, leading eventually to breakdown of the bond coat. The 8.9 percent Y2O3 coating performed best because the as-sprayed metastable tetragonal phase converted slowly into the low-Y2O3 tetragonal plus high-Y2O3 cubic-phase mixture, so that the deleterious monoclinic phase was inhibited from forming. Failure appeared to start with the formation of circumferential cracks in the zirconia, probably due to compressive stresses during cooling, followed by the formation of radial cracks due to tensile stresses during heating. Cracks appeared to initiate at the Al2O3 scale/bond coat interface and propagate through the zirconia coating. Comparisons were made with the behavior of bulk ZrO2-Y2O3 and the relationship between the microstructure of the tetragonal phase and the phase diagram. A separate investigation was also made of the ZrO2-Al2O3 interface.

  5. Tungstated zirconia as promising carrier for DeNOx catalysts with improved resistance towards alkali poisoning

    DEFF Research Database (Denmark)

    Due-Hansen, Johannes; Kustov, Arkadii; Rasmussen, Søren Birk

    2006-01-01

    of new alternative catalysts that are more resistant towards poisoning with potassium. Vanadia-based catalysts supported on traditional and tungstated zirconia has been prepared and tested in selective catalytic reduction of NO with ammonia. All prepared catalysts were characterized using N2-BET, XRD...... on the crystallinity of the zirconia and on the surface acidity. Vanadia supported on tungstated zirconia calcined at 700 8C revealed superior catalytic performance and resistance towards alkali poisoning in comparison with a traditional catalyst. The improved poisoning resistance of the samples based on tungstated...

  6. Fabrication and Performance of Zirconia Electrolysis Cells for Cabon Dioxide Reduction for Mars In Situ Resource Utilization Applications

    Science.gov (United States)

    Minh, N. Q.; Chung, B. W.; Doshi, R.; Lear, G. R.; Montgomery, K.; Ong, E. T.

    1999-01-01

    Use of the Martian atmosphere (95% CO2) to produce oxygen (for propellant and life support) can significantly lower the required launch mass and dramatically reduce the total cost for Mars missions. Zirconia electrolysis cells are one of the technologies being considered for oxygen generation from carbon dioxide in Mars In Situ Resource Utilization (ISRU) production plants. The attractive features of the zirconia cell for this application include simple operation and lightweight, low volume system. A zirconia electrolysis cell is an all-solid state device, based on oxygen-ion conducting zirconia electrolytes, that electrochemically reduces carbon dioxide to oxygen and carbon monoxide. The cell consists of two porous electrodes (the anode and cathode) separated by a dense zirconia electrolyte. Typical zirconia cells contain an electrolyte layer which is 200 to 400 micrometer thick. The electrical conductivity requirement for the electrolyte necessitates an operating temperature of 9000 to 10000C. Recently, the fabrication of zirconia cells by the tape calendering has been evaluated. This fabrication process provides a simple means of making cells having very thin electrolytes (5 to 30 micrometers). Thin zirconia electrolytes reduce cell ohmic losses, permitting efficient operation at lower temperatures (8000C or below). Thus, tape-calendered cells provides not only the potential of low temperature operation but also the flexibility in operating temperatures. This paper describes the fabrication of zirconia cells by the tape calendering method and discusses the performance results obtained to date.

  7. Zirconia implants and peek restorations for the replacement of upper molars.

    Science.gov (United States)

    Parmigiani-Izquierdo, José María; Cabaña-Muñoz, María Eugenia; Merino, José Joaquín; Sánchez-Pérez, Arturo

    2017-12-01

    One of the disadvantages of the zirconia implants is the lack of elasticity, which is increased with the use of ceramic or zirconia crowns. The consequences that could result from this lack of elasticity have led to the search for new materials with improved mechanical properties. A patient who is a 45-year-old woman, non-smoker and has no medical record of interest with a longitudinal fracture in the palatal root of molar tooth 1.7 and absence of tooth 1.6 was selected in order to receive a zirconia implant with a PEEK-based restoration and a composite coating. The following case report describes and analyses treatment with zirconia implants in molars following a flapless surgical technique. Zirconia implants are an alternative to titanium implants in patients with allergies or who are sensitive to metal alloys. However, one of the disadvantages that they have is their lack of elasticity, which increases with the use of ceramic or zirconia crowns. The consequences that can arise from this lack of elasticity have led to the search for new materials with better mechanical properties to cushion occlusal loads. PEEK-based restoration in implant prosthetics can compensate these occlusal forces, facilitating cushioning while chewing. This procedure provides excellent elasticity and resembles natural tooth structure. This clinical case suggests that PEEK restorations can be used in zirconia implants in dentistry.

  8. Is zirconia a viable alternative to titanium for oral implant? A critical review.

    Science.gov (United States)

    Sivaraman, Karthik; Chopra, Aditi; Narayan, Aparna I; Balakrishnan, Dhanasekar

    2017-08-17

    Titanium based implant systems, though considered as the gold standard for rehabilitation of edentulous spaces, have been criticized for many inherent flaws. The onset of hypersensitivity reactions, biocompatibility issues, and an unaesthetic gray hue have raised demands for more aesthetic and tissue compatible material for implant fabrication. Zirconia is emerging as a promising alternative to conventional Titanium based implant systems for oral rehabilitation with superior biological, aesthetics, mechanical and optical properties. This review aims to critically analyze and review the credibility of Zirconia implants as an alternative to Titanium for prosthetic rehabilitation. The literature search for articles written in the English language in PubMed and Cochrane Library database from 1990 till December 2016. The following search terms were utilized for data search: "zirconia implants" NOT "abutment", "zirconia implants" AND "titanium implants" AND "osseointegration", "zirconia implants" AND compatibility. The number of potential relevant articles selected were 47. All the human in vivo clinical, in vitro, animals' studies were included and discussed under the following subheadings: Chemical composition, structure and phases; Physical and mechanical properties; Aesthetic and optical properties; Osseointegration and biocompatibility; Surface modifications; Peri-implant tissue compatibility, inflammation and soft tissue healing, and long-term prognosis. Zirconia implants are a promising alternative to titanium with a superior soft-tissue response, biocompatibility, and aesthetics with comparable osseointegration. However, further long-term longitudinal and comparative clinical trials are required to validate zirconia as a viable alternative to the titanium implant. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  9. Zirconia implants and peek restorations for the replacement of upper molars

    Directory of Open Access Journals (Sweden)

    José María Parmigiani-Izquierdo

    2017-02-01

    Full Text Available Abstract Background One of the disadvantages of the zirconia implants is the lack of elasticity, which is increased with the use of ceramic or zirconia crowns. The consequences that could result from this lack of elasticity have led to the search for new materials with improved mechanical properties. Case presentation A patient who is a 45-year-old woman, non-smoker and has no medical record of interest with a longitudinal fracture in the palatal root of molar tooth 1.7 and absence of tooth 1.6 was selected in order to receive a zirconia implant with a PEEK-based restoration and a composite coating. The following case report describes and analyses treatment with zirconia implants in molars following a flapless surgical technique. Zirconia implants are an alternative to titanium implants in patients with allergies or who are sensitive to metal alloys. However, one of the disadvantages that they have is their lack of elasticity, which increases with the use of ceramic or zirconia crowns. The consequences that can arise from this lack of elasticity have led to the search for new materials with better mechanical properties to cushion occlusal loads. PEEK-based restoration in implant prosthetics can compensate these occlusal forces, facilitating cushioning while chewing. Conclusion This procedure provides excellent elasticity and resembles natural tooth structure. This clinical case suggests that PEEK restorations can be used in zirconia implants in dentistry.

  10. Pro-inflammatory cytokines at zirconia implants and teeth. A cross-sectional assessment.

    Science.gov (United States)

    Cionca, Norbert; Hashim, Dena; Cancela, Jose; Giannopoulou, Catherine; Mombelli, Andrea

    2016-11-01

    The aim of this study was to compare the expression of host-derived markers in peri-implant/gingival crevicular fluid (PCF/GCF) and clinical conditions at ceramic implants and contralateral natural teeth. As a secondary objective, we compared zirconia implants with titanium implants. One zirconia implant (ZERAMEX® Implant System) and one contralateral natural tooth were examined in 36 systemically healthy subjects (21 males, 15 females, mean age 58). The levels of Il-1β, Il-1RA, Il-6, Il-8, Il-17, b-FGF, G-CSF, GM-CSF, IFNɣ, MIP-1β, TNF-α, and VEGF were assessed in PCF/GCF using the Bio-Plex 200 Suspension Array System. The plaque index (PI), gingival index (GI), probing depth (PD), and bleeding on probing (BOP) were assessed at six sites around each implant or tooth. Titanium implants were also assessed when present (n = 9). The zirconia implants were examined after a loading period of at least 1.2 years (average 2.2 years). The mean PI was significantly lower at zirconia implants compared to teeth (p = 0.003), while the mean GI, PD, and BOP were significantly higher (p zirconia implants and teeth. The levels of IL-1β and TNF-α were significantly higher at zirconia implants than at teeth. No significant differences were found between zirconia and titanium implants. A correlation was found between the levels of IL-1RA, IL-8, GM-CSF, and MIP-1β at zirconia and titanium implants. The correlation in the expression of five biomarkers at zirconia implants and teeth, and of four biomarkers at zirconia and titanium implants, is compatible with the existence of a patient-specific inflammatory response pattern. Higher mean GI, PD, and BOP around implants suggests that the peri-implant mucosa may be mechanically more fragile than the gingiva. Similar expression of selected biomarkers at zirconia implants and teeth and at zirconia and titanium implants reflects existence of patient-specific inflammatory response patterns.

  11. Formation of metastable tetragonal zirconia nanoparticles: Competitive influence of the dopants and surface state

    Energy Technology Data Exchange (ETDEWEB)

    Gorban, Oksana, E-mail: matscidep@aim.com [Donetsk Institute for Physics and Engineering named after A.A. Galkin of the NAS of Ukraine, Nauki av. 46, Kyiv 03680 (Ukraine); Synyakina, Susanna; Volkova, Galina; Gorban, Sergey; Konstantiova, Tetyana [Donetsk Institute for Physics and Engineering named after A.A. Galkin of the NAS of Ukraine, Nauki av. 46, Kyiv 03680 (Ukraine); Lyubchik, Svetlana, E-mail: s_lyubchik@yahoo.com [REQUIMTE, Universida de Nova de Lisboa, 2829-516 Caparica (Portugal)

    2015-12-15

    The effect of the surface modification of the nanoparticles of amorphous and crystalline partially stabilized zirconia by fluoride ions on stability of the metastable tetragonal phase was investigated. Based on the DSC, titrimetry and FTIR spectroscopy data it was proven that surface modification of the xerogel resulted from an exchange of the fluoride ions with the basic OH groups. The effect of the powder pre-calcination temperature before modification on the formation of metastable tetragonal phase in partially stabilized zirconia was investigated. It was shown that the main factor of tetragonal zirconia stabilization is the state of nanoparticles surface at pre-crystallization temperatures.

  12. Effect of accelerated aging on translucency of monolithic zirconia

    Directory of Open Access Journals (Sweden)

    O. Abdelbary

    2016-12-01

    Conclusion: Thickness of zirconia has significant effect on translucency. Aging has significant effect on thinner sections of zirconia. More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration.

  13. Osseointegration of zirconia implants: an SEM observation of the bone-implant interface

    Directory of Open Access Journals (Sweden)

    Naujoks Christian

    2008-11-01

    Full Text Available Abstract Background The successful use of zirconia ceramics in orthopedic surgery led to a demand for dental zirconium-based implant systems. Because of its excellent biomechanical characteristics, biocompatibility, and bright tooth-like color, zirconia (zirconium dioxide, ZrO2 has the potential to become a substitute for titanium as dental implant material. The present study aimed at investigating the osseointegration of zirconia implants with modified ablative surface at an ultrastructural level. Methods A total of 24 zirconia implants with modified ablative surfaces and 24 titanium implants all of similar shape and surface structure were inserted into the tibia of 12 Göttinger minipigs. Block biopsies were harvested 1 week, 4 weeks or 12 weeks (four animals each after surgery. Scanning electron microscopy (SEM analysis was performed at the bone implant interface. Results Remarkable bone attachment was already seen after 1 week which increased further to intimate bone contact after 4 weeks, observed on both zirconia and titanium implant surfaces. After 12 weeks, osseointegration without interposition of an interfacial layer was detected. At the ultrastructural level, there was no obvious difference between the osseointegration of zirconia implants with modified ablative surfaces and titanium implants with a similar surface topography. Conclusion The results of this study indicate similar osseointegration of zirconia and titanium implants at the ultrastructural level.

  14. Bonding of Resin Cement to Zirconia with High Pressure Primer Coating

    Science.gov (United States)

    Wang, Ying-jie; Jiao, Kai; Liu, Yan; Zhou, Wei; Shen, Li-juan; Fang, Ming; Li, Meng; Zhang, Xiang; Tay, Franklin R.; Chen, Ji-hua

    2014-01-01

    Objectives To investigate the effect of air-drying pressure during ceramic primer coating on zirconia/resin bonding and the surface characteristics of the primed zirconia. Methods Two ceramic primers (Clearfil Ceramic Primer, CCP, Kuraray Medical Inc. and Z-Prime Plus, ZPP, Bisco Inc.) were applied on the surface of air-abraded zirconia (Katana zirconia, Noritake) and dried at 4 different air pressures (0.1–0.4 MPa). The primed zirconia ceramic specimens were bonded with a resin-based luting agent (SA Luting Cement, Kuraray). Micro-shear bond strengths of the bonded specimens were tested after 3 days of water storage or 5,000× thermocycling (n = 12). Failure modes of the fractured specimens were examined with scanning electron miscopy. The effects of air pressure on the thickness of the primer layers and the surface roughness (Sa) of primed zirconia were evaluated using spectroscopic ellipsometry (n = 6), optical profilometry and environmental scanning electron microscopy (ESEM) (n = 6), respectively. Results Clearfil Ceramic Primer air-dried at 0.3 and 0.4 MPa, yielding significantly higher µSBS than gentle air-drying subgroups (pzirconia bond strength and durability significantly. Higher air-drying pressure (0.3-0.4 MPa) for CCP and intermediate pressure (0.2 MPa) for ZPP are recommended to produce strong, durable bonds between resin cement and zirconia ceramics. PMID:24992678

  15. Clinical and patient-reported outcomes of zirconia-based implant fixed dental prostheses: Results of a prospective case series 5 years after implant placement.

    Science.gov (United States)

    Spies, Benedikt Christopher; Witkowski, Siegbert; Vach, Kirstin; Kohal, Ralf-Joachim

    2018-01-01

    To evaluate the clinical and patient-reported outcome of all-ceramic zirconia implant supported fixed dental prostheses (FDPs) 5 years after implant installation. Thirteen patients were treated with two terminally placed one-piece zirconia implants for a three-unit FDP each. The FDPs consisted of a CAD/CAM-fabricated zirconia framework over-pressed with a fluor-apatite veneering ceramic and were adhesively cemented. Survival and success were assessed by applying modified US Public Health Service (USPHS) criteria and preparation of Kaplan-Meier (KM) plots. Alpha and Bravo ratings were accepted for success (among others including small area veneer chippings and occlusal roughness), whereas Charlie ratings allowing for intra-oral correction (e.g., polishing) were accepted for survival. Furthermore, patient-reported outcome measures (PROMs) were analyzed with the help of visual analogue scales (VAS). Wilcoxon matched-pairs signed-rank test (USPHS criteria) and linear mixed models (PROMs) were used to evaluate time effects on response variables. All patients were available 61.8 ± 1.1 months after implant installation (53.6 ± 3.1 months after final prosthesis insertion). FDP survival was 100%. Significant incidence of veneer chipping (p = .0096) and occlusal roughness (p = .0019) was observed. Charlie rated extent of both phenomena resulted in a KM success estimate of 38.5% (95% CI: 14.1%-62.8%; seven FDPs with obvious roughness, three of them with extended veneer chipping). Compared with the pre-treatment assessments (30%-81% of satisfaction), all surveys at prosthetic delivery showed significantly improved VAS scores (66%-93%; p ≤ .038), except for speech (p = .341). Concerning function, esthetics and self-esteem, no decrease in satisfaction could be observed until the end of follow-up (90%-96%; p ≥ .057), whereas perception of sense (92%) and speech (95%) increased over time (p ≤ .030). Occurrence of technical complications did not correlate

  16. Prosthetically guided bone sculpturing for a maxillary complete-arch implant-supported monolithic zirconia fixed prosthesis based on a digital smile design: A clinical report.

    Science.gov (United States)

    Rojas-Vizcaya, Fernando

    2017-11-01

    A digital smile design was used to create an average smile and to develop a removable interim restoration for an edentulous patient with a high smile line and different bone levels in the maxilla. The interim restoration was used as a guide to perform bone sculpturing to create space for the biological width and to restore a monolithic zirconia implant-supported fixed restoration. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  17. Evaluation of experimental coating to improve the zirconia-veneering ceramic bond strength.

    Science.gov (United States)

    Matani, Jay D; Kheur, Mohit; Jambhekar, Shantanu Subhashchandra; Bhargava, Parag; Londhe, Aditya

    2014-12-01

    To evaluate the shear bond strength (SBS) between zirconia and veneering ceramic following different surface treatments of zirconia. The efficacy of an experimental zirconia coating to improve the bond strength was also evaluated. Zirconia strips were fabricated and were divided into four groups as per their surface treatment: polished (control), airborne-particle abrasion, laser irradiation, and application of the experimental coating. The surface roughness and the residual monoclinic content were evaluated before and after the respective surface treatments. A scanning electron microscope (SEM) analysis of the experimental surfaces was performed. All specimens were subjected to shear force in a universal testing machine. The SBS values were analyzed with one-way ANOVA followed by Bonferroni post hoc for groupwise comparisons. The fractured specimens were examined to observe the failure mode. The SBS (29.17 MPa) and roughness values (0.80) of the experimental coating group were the highest among the groups. The residual monoclinic content was minimal (0.32) when compared to the remaining test groups. SEM analysis revealed a homogenous surface well adhered to an undamaged zirconia base. The other test groups showed destruction of the zirconia surface. The analysis of failure following bond strength testing showed entirely cohesive failures in the veneering ceramic in all study groups. The experimental zirconia surface coating is a simple technique to increase the microroughness of the zirconia surface, and thereby improve the SBS to the veneering ceramic. It results in the least monoclinic content and produces no structural damage to the zirconia substructure. © 2014 by the American College of Prosthodontists.

  18. Thermodynamics of tetragonal zirconia formation in a nanolaminate film

    Science.gov (United States)

    Aita, C. R.; Wiggins, M. D.; Whig, R.; Scanlan, C. M.; Gajdardziska-Josifovska, M.

    1996-01-01

    Zirconia-alumina transformation-toughening nanolaminates were fabricated by reactive sputter deposition. The average crystallite size and volume fraction of each zirconia polymorph were determined by x-ray diffraction. The volume fraction of tetragonal zirconia, the phase necessary for transformation toughening, was found to strongly depend upon the zirconia layer thickness. An end-point thermodynamics model involving hemispherical cap zirconia crystallites was developed to explain this phenomenon. In excellent agreement with experimental results, the model predicts that unity volume fraction of tetragonal zirconia is produced in the nanolaminate when the zirconia layer thickness is less than the radius at which a growing zirconia crystallite spontaneously transforms to the monoclinic phase.

  19. Fabrication and properties of yttria, ceria doped zirconia-aluminia ceramic composites

    International Nuclear Information System (INIS)

    Lyubushkin, R.A.; Ivanov, O.N.; Chuev, V.P.; Buzov, A.A.

    2011-01-01

    At present, zirconia-based ceramics are gaining popularity in dentistry, particularly in fixed prosthodontics. clinically, it is important that ceramic restorations reproduce the translucency and color of natural teeth. Zirconia based ceramics is a high performance material with excellent biocompatibility and mechanical properties, which suggest its suitability for posterior fixed partial dentures. Y 2 O 3 -stabilized tetragonal zirconia polycrystalline (YTZ/Al 2 O 3 ) and CeO 2 -stabilized tetragonal zirconia polycrystalline (CZA) ceramics with high-performance were prepared for dental application by use the wet chemical route, consolidated by cold isostatic pressing, and two-step sintering method. Physical and mechanical properties test results show that the bending strength, fracture toughness, and the density of full sintered ceramics suggest that the material is relatively suitable for dental restoration.

  20. Adhesion/cementation to zirconia and other non-silicate ceramics: Where are we now?

    Science.gov (United States)

    Thompson, Jeffrey Y; Stoner, Brian R.; Piascik, Jeffrey R.; Smith, Robert

    2010-01-01

    Non-silicate ceramics, especially zirconia, have become a topic of great interest in the field of prosthetic and implant dentistry. A clinical problem with use of zirconia-based components is the difficulty in achieving suitable adhesion with intended synthetic substrates or natural tissues. Traditional adhesive techniques used with silica-based ceramics do not work effectively with zirconia. Currently, several technologies are being utilized clinically to address this problem, and other approaches are under investigation. Most focus on surface modification of the inert surfaces of high strength ceramics. The ability to chemically functionalize the surface of zirconia appears to be critical in achieving adhesive bonding. This review will focus on currently available approaches as well as new advanced technologies to address this problem. PMID:21094526

  1. Shear bond strength of veneering porcelain to zirconia and metal cores

    Science.gov (United States)

    Choi, Bu-Kyung; Yang, Jae-Ho; Lee, Jai-Bong; Kim, Sung-Hun

    2009-01-01

    STATEMENT OF PROBLEM Zirconia-based restorations have the common technical complication of delamination, or porcelain chipping, from the zirconia core. Thus the shear bond strength between the zirconia core and the veneering porcelain requires investigation in order to facilitate the material's clinical use. PURPOSE The purpose of this study was to evaluate the bonding strength of the porcelain veneer to the zirconia core and to other various metal alloys (high noble metal alloy and base metal alloy). MATERIAL AND METHODS 15 rectangular (4×4×9mm) specimens each of zirconia (Cercon), base metal alloy (Tillite), high noble metal alloy (Degudent H) were fabricated for the shear bond strength test. The veneering porcelain recommended by the manufacturer for each type of material was fired to the core in thickness of 3mm. After firing, the specimens were embedded in the PTFE mold, placed on a mounting jig, and subjected to shear force in a universal testing machine. Load was applied at a crosshead speed of 0.5mm/min until fracture. The average shear strength (MPa) was analyzed with the one-way ANOVA and the Tukey's test (α= .05). The fractured specimens were examined using SEM and EDX to determine the failure pattern. RESULTS The mean shear strength (± SD) in MPa was 25.43 (± 3.12) in the zirconia group, 35.87 (± 4.23) in the base metal group, 38.00 (± 5.23) in the high noble metal group. The ANOVA showed a significant difference among groups, and the Tukey's test presented a significant difference between the zirconia group and the metal group. Microscopic examination showed that the failure primarily occurred near the interface with the residual veneering porcelain remaining on the core. CONCLUSION There was a significant difference between the metal ceramic and zirconia ceramic group in shear bond strength. There was no significant difference between the base metal alloy and the high noble metal alloy. PMID:21165268

  2. Dilemmas in zirconia bonding: A review

    Directory of Open Access Journals (Sweden)

    Obradović-Đuričić Kosovka

    2013-01-01

    Full Text Available This article presents a literature review on the resin bond to zirconia ceramic. Modern esthetic dentistry has highly recognized zirconia, among other ceramic materials. Biocompatibility of zirconia, chemical and dimensional stability, excellent mechanical properties, all together could guarantee optimal therapeutical results in complex prosthodontic reconstruction. On the other hand, low thermal degradation, aging of zirconia as well as problematic bonding of zirconia framework to dental luting cements and tooth structures, opened the room for discussion concerning their clinical durability. The well known methods of mechanical and chemical bonding used on glass-ceramics are not applicable for use with zirconia. Therefore, under critical clinical situations, selection of the bonding mechanism should be focused on two important points: high initial bond strength value and long term bond strength between zirconia-resin interface. Also, this paper emphases the use of phosphate monomer luting cements on freshly air-abraded zirconia as the simplest and most effective way for zirconia cementation procedure today.

  3. Lava zirconia crowns and bridges.

    Science.gov (United States)

    Suttor, D

    2004-01-01

    Ceramic restorations--suitable for the anterior as well as the posterior region, simultaneously satisfying the demand for high strength, longevity, and esthetics--are an increasingly important field for the dental professional. Because of its outstanding mechanical properties and esthetics with a proven track record in other industrial areas, zirconium oxide (zirconia) is emerging in the dental industry. As the manufacturing method of choice, CAD/CAM is important for the dental laboratory; however, in the final analysis, the primary focus will be on the material properties and the clinical performance of the result of the CAD/CAM process--in this case, zirconia crowns and bridges. This is especially true since some concepts do not require the acquisition of a CAD/CAM system at all.

  4. Alumina-Reinforced Zirconia Composites

    Science.gov (United States)

    Choi, Sung R.; Bansal, Narottam P.

    2003-01-01

    Alumina-reinforced zirconia composites, used as electrolyte materials for solid oxide fuel cells, were fabricated by hot pressing 10 mol percent yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina particulates and platelets each containing 0 to 30 mol percent alumina. Major mechanical and physical properties of both particulate and platelet composites including flexure strength, fracture toughness, slow crack growth, elastic modulus, density, Vickers microhardness, thermal conductivity, and microstructures were determined as a function of alumina content either at 25 C or at both 25 and 1000 C. Flexure strength and fracture toughness at 1000 C were maximized with 30 particulate and 30 mol percent platelet composites, respectively, while resistance to slow crack growth at 1000 C in air was greater for 30 mol percent platelet composite than for 30 mol percent particulate composites.

  5. Zirconia-molybdenum disilicide composites

    Science.gov (United States)

    Petrovic, John J.; Honnell, Richard E.

    1991-01-01

    Compositions of matter comprised of molybdenum disilicide and zirconium oxide in one of three forms: pure, partially stabilized, or fully stabilized and methods of making the compositions. The stabilized zirconia is crystallographically stabilized by mixing it with yttrium oxide, calcium oxide, cerium oxide, or magnesium oxide and it may be partially stabilized or fully stabilized depending on the amount of stabilizing agent in the mixture.

  6. Determination of residual zirconia in the reaction product of zircon formation from zirconia and silica

    International Nuclear Information System (INIS)

    Hashiba, Minoru; Miura, Eiji; Nurishi, Yukio; Hibino, Taizo

    1978-01-01

    A new chemical method for the determination of zirconia in the reaction product of zircon formation from zirconia and silica is presented in this paper. The reaction product was fused in the temperature range between 400 0 C, and 450 0 C by ammonium sulfate (zirconia/ammonium sulfate = 1/10, weight). Zirconia was extracted by 4N H 2 SO 4 aqueous solution. After the residue was separated by filter paper containing filter pulp, it was washed by hot water thoroughly. By adding aqueous ammonia water to the combined filtrate, zirconium hydroxide was precipitated gelatinously. The precipitate was ignited in platinum crucible at 1000 0 C and the zirconia obtained was weighed. It was confirmed by the following experiments that the present method is very reliable for quantitative determination of residual zirconia. Firstly, in both zirconia and various mixtures of zircon and silica, the recovery of zirconia is about (99.6 +- 0.2)%. Secondly, the reaction for equimolar mixture of zirconia and silica was conducted at several temperatures between 1350 0 C and 1500 0 C. The quantity of residual zirconia on the way of the reaction was reasonably determined by the present method. In conclusion, the present method can be applicable for the study on the reaction mechanism of zircon formation from zirconia and silica. (auth.)

  7. Microstructural stability of zirconia-alumina composite coatings during hot corrosion test at 1050 {sup o}C

    Energy Technology Data Exchange (ETDEWEB)

    Keyvani, A., E-mail: akeyvani@ut.ac.i [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Saremi, M., E-mail: saremi@ut.ac.i [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Heydarzadeh Sohi, M., E-mail: mhsohi@ut.ac.i [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of)

    2010-09-10

    In the present work hot corrosion behavior of plasma sprayed zirconia-alumina coatings on Ni-base, IN-738, super alloy substrate was studied compared with normal zirconia. Hot corrosion resistance of the coatings was measured at 1050 {sup o}C using an atmospheric electrical furnace and a fused mixture of vanadium pentoxide and sodium sulfate salt. The hot corrosion test duration was 4 h in each cycle, while the specimens were cooled in the furnace. The general and peripheral conditions of the specimens were inspected. If there were any cracks or spallation in coating wedge the test was stopped, the time was recorded and coating microstructure was studied. Composite coatings of zirconia-alumina having alumina as a top coat or a mixed zirconia-alumina layer, showed better resistance in hot corrosion tests. It was concluded that alumina overlay on zirconia has promoted the hot corrosion resistance of the coatings.

  8. Zirconia enrichment in zircon sand by selective fungus-mediated bioleaching of silica.

    Science.gov (United States)

    Bansal, Vipul; Syed, Asad; Bhargava, Suresh K; Ahmad, Absar; Sastry, Murali

    2007-04-24

    One of the important routes for the production of zirconia is by chemical treatment and removal of silica from zircon sand (ZrSixOy). We present here a completely green chemistry approach toward enrichment of zirconia in zircon sand; this is based on the reaction of the fungus Fusarium oxysporum with zircon sand by a process of selective extracellular bioleaching of silica nanoparticles. Since this reaction does not result in zirconia being simultaneously leached out from the sand, there is a consequent enrichment of the zirconia component in zircon sand. We believe that fungal enzymes specifically hydrolyze the silicates present in the sand to form silicic acid, which on condensation by certain other fungal enzymes results in room-temperature synthesis of silica nanoparticles. This fungus-mediated twofold approach might have vast commercial implications in low-cost, ecofriendly, room-temperature syntheses of technologically important oxide nanomaterials from potentially cheap naturally available raw materials like zircon sand.

  9. Spectrophotometric analysis of fluorescent zirconia abutments compared to "conventional" zirconia abutments: A within subject controlled clinical trial.

    Science.gov (United States)

    Thoma, Daniel S; Gamper, Felix B; Sapata, Vítor M; Voce, Giuseppe; Hämmerle, Christoph H F; Sailer, Irena

    2017-08-01

    Zirconia abutments are frequently used for implant-supported single crowns. Even though demonstrating esthetic benefits compared to metal abutments, zirconia abutments lead to an increased brightness of the peri-implant mucosa compared to natural teeth and are not ideal from an esthetic point of view. To test whether or not a fluorescent hybrid zirconia abutment offers superior esthetics compared to a non-fluorescent one-piece zirconia abutment based on spectrophotometric analysis. In 24 patients with 24 single-tooth implants, 2 types of reconstructions were fabricated: a directly veneered one-piece zirconia abutment/crown (control) and a directly veneered fluorescent hybrid zirconia abutment/crown (test). Spectrophotometric assessment was performed: prior to abutment insertion (WA), at abutment try-in (A), at the try-in of the final crowns (C). Color differences (ΔE) were assessed compared to the gingiva of natural teeth (T) and between the reconstructions. At abutment try-in, ΔE values were 8.49 ± 3.59 for A Control and 8.27 ± 4.03 for A Test compared to T. At crown insertion, ΔE values were 7.61 ± 4.03 for C Control and 8.32 ± 3.57 for C Test compared to T. The difference in ΔE values between A Control and A Test was 0.23 ± 2.54 (P = .37), whereas the difference in ΔE values between C Control and C Test was -0.66 ±3.45 (P = .48). For all cases with a mucosal thickness ≤2 mm, the comparison between C Control and C Test was significant in favor of the control group (P = .03). Both types of reconstructions were similar in terms of esthetics. Incases with a mucosal thickness of compared to the natural gingiva was more pronounced for the fluorescent hybrid zirconia reconstructions. © 2017 Wiley Periodicals, Inc.

  10. Development of a nano structured system based on zirconia and Co nanoparticles for thermoluminescent applications: sensor of gamma and UV radiation; Desarrollo de un sistema nanoestructurado a base de zirconia y nanoparticulas de Co para aplicaciones termoluminiscentes: sensor de radiacion gamma y UV

    Energy Technology Data Exchange (ETDEWEB)

    Villa S, G.

    2014-07-01

    Powders of zirconium IV oxide as well as systems composed of zirconia nano crystals and cobalt nanoparticles (ZrO{sub 2}:NPCo) with dimensions of nanometers were synthesized by the sol-gel method. Zirconia and ZrO{sub 2}:NPCo systems have crystalline structure tetragonal or monoclinic is the heat treatment was to 500 and 1000 degrees Celsius respectively. The characterization of the synthesized materials consisted of a morphological and structural analysis, the information obtained was correlated to its thermoluminescent response induced by gamma and ultraviolet radiation. Thermoluminescent behavior was analyzed on different concentrations of cobalt nanoparticles incorporated during the synthesis process of the zirconium oxide. The monoclinic structure has the highest sensitivity thermoluminescent induced by ultraviolet and gamma radiation. Moreover, the thermoluminescence intensity decreased considerably in ZrO{sub 2}:NPCo systems and was induced the growth of a glow peak at 280 degrees Celsius. In most of the materials analyzed the relation of the thermoluminescence intensity depending the time of irradiation with ultraviolet light showed the saturation of the traps in the material after 60 s of irradiation. Using gamma radiation is observed a behavior linear in the applied dose range between 0.25 Gy and 450 Gy. The growth of a glow peak at 280 degrees Celsius is the most important change in the thermoluminescence characteristics of zirconia. The ZrO{sub 2}:NPCo systems can be used in the development of thermoluminescent dosimeters for detecting gamma radiation fields mainly. (Author)

  11. Surface degradation of nanocrystalline zirconia dental implants

    NARCIS (Netherlands)

    Ocelík, Václav; Schepke, Ulf; Rasoul, Hamid Haji; Cune, Marco S.; De Hosson, Jeff Th M.

    2017-01-01

    Yttria-stabilized zirconia prepared by hot isostatic pressing represents attractive material for biomedical applications. In this work the degradation of yttria-stabilized zirconia dental implants abutments due to the tetragonal to monoclinic phase transformation after one year of clinical use was

  12. Enamel wear opposing polished and aged zirconia.

    Science.gov (United States)

    Burgess, J O; Janyavula, S; Lawson, N C; Lucas, T J; Cakir, D

    2014-01-01

    Aging of dental zirconia roughens its surface through low temperature degradation. We hypothesized that age-related roughening of zirconia crowns may cause detrimental wear to the enamel of an opposing tooth. To test our hypothesis, we subjected artificially aged zirconia and reference specimens to simulated mastication in a wear device and measured the wear of an opposing enamel cusp. Additionally, the roughness of the pretest surfaces was measured. The zirconia specimens, artificially aged by autoclave, showed no significant increase in roughness compared to the nonaged specimens. Furthermore, no significant difference in material or opposing enamel wear between the aged and nonaged zirconia was seen. All zirconia specimens showed less material and opposing enamel wear than the enamel to enamel control or veneering porcelain specimens. Scanning electron micrographs showed relatively smooth surfaces of aged and nonaged zirconia following wear testing. The micrographs of the veneering ceramic showed sharp fractured edges and fragments of wear debris. Zirconia may be considered a wear-friendly material for restorations opposing enamel, even after simulated aging.

  13. Sintering of zirconia in high-pressure

    International Nuclear Information System (INIS)

    Kunrath, A.O.; Strohaecker, T.R.; Pereira, A.S.; Jornada, J.A.H. da; Piermarini, G.J.

    1989-01-01

    A systematic study about the sintering of zirconia hyperfines powders in high-pressure is presented. The differents conditions effect of sintering in microstructure and in hardness and tenacity properties of zirconia samples with a very fine grain is also studied. (C.G.C.) [pt

  14. Zirconia-fluorapatite materials produced by HIP.

    Science.gov (United States)

    Adolfsson, E; Hermansson, L

    1999-07-01

    Composites of tetragonal zirconia and fluorapatite were sealed in steel tubes and hot isostatically pressed at 1200 degrees C. The phases formed in the samples were evaluated by X-ray powder diffraction. When the composites contained larger amounts of fluorapatite, the tetragonal zirconia changed gradually into the cubic phase with decreasing zirconia content. These phase changes occurred due to a transfer of calcium from fluorapatite, which acted as an additional dopant in zirconia. Small amounts of monoclinic zirconia were also present in all samples. The cell dimension in fluorapatite was changed with the composition of the composite. However, decomposition of the fluorapatite was not possible to detect. Vickers hardness and fracture toughness were measured and ranged from 5.1 to 10.8 GPa and 0.9-5.5 MPam1/2, respectively. Microstructures in the composites were studied with scanning electron microscopy.

  15. Zirconia ceramic post systems: a literature review and a case report.

    Science.gov (United States)

    Ozkurt, Zeynep; Işeri, Ufuk; Kazazoğlu, Ender

    2010-05-01

    Cast metal post-core systems have a long history of successful use because of their superior physical properties. However, their high elastic modulus can cause stress concentrations within the surrounding radicular dentin, resulting in root fractures. Moreover, the increasing demand for more esthetically appealing and biocompatible restorations has led to the development of tooth-colored, translucent, metal-free post-core systems. Notably, prefabricated zirconia ceramic post systems have been introduced to satisfy this trend toward a heightened awareness of esthetics, whereby the translucency of all-ceramic crowns can be successfully maintained with the use of ceramic post-core materials. Owing to the keen interest in and widespread use of zirconia ceramic post systems, many in vitro studies on zirconia posts have been published in the last 15 years. The aim of this article was to present data about the retention, fracture resistance, microleakage, light transmission, esthetic advantages, and radiodensity of zirconia posts. Two clinical survival rate studies were also presented. Based on the results of these studies, zirconia posts have been shown to improve the esthetic quality of all ceramic crowns and thus their usage is recommended. Apart from literature review, a case report in which a fractured fiber post was replaced with a custom-made zirconia post was also presented.

  16. Raman spectroscopic analysis of phase-transformation and stress patterns in zirconia hip joints.

    Science.gov (United States)

    Pezzotti, Giuseppe; Porporati, Alessandro A

    2004-01-01

    Confocal Raman piezo-spectroscopy has been used for the quantitative assessments of phase transformation and residual stresses in zirconia made artificial hip joints. This work can be considered to be a first step towards the development of a fully quantitative technique for the spectroscopic characterization of zirconia femoral heads and other zirconia parts for biomedical applications. After establishing reliable calibration procedures, Raman microprobe spectroscopy could be extended to provide quantitative assessments of zirconia metastability and microscopic stress fields along the z axis perpendicular to the joint surface. For the first time, we have directly visualized patterns of phase-transformation and related residual stresses on the very surface and along the subsurface of both in vitro tested and retrieved hip implants. These spectroscopic assessments may open a completely new perspective in understanding the micromechanical wear behavior of zirconia ceramics in biological environment and in developing new zirconia-based biomaterials with superior stability characteristics. (c) 2004 Society of Photo-Optical Instrumentation Engineers.

  17. Reactions of yttria-stabilized zirconia with oxides and sulfates of various elements

    Science.gov (United States)

    Zaplatynsky, I.

    1978-01-01

    The reactions between partially stabilized zirconia, containing 8 weight-percent yttria, and oxides and sulfates of various elements were studied at 1200, 1300, and 1400 C for times to 800, 400, and 200 hours, respectively. These oxides and sulfates represent impurities and additives potentially present in gas turbine fuels or impurities in the turbine combustion air as well as the elements of the substrate alloys in contact with zirconia. Based on the results, these compounds can be classified in four groups: (1) compounds which did not react with zirconia (Na2SO4, K2SO4, Cr2O3, Al2O3 and NiO); (2) compounds that reached completely with both zirconia phases (CaO, BaO, and BaSO4); (3) compounds that reacted preferentially with monoclinic zirconia (Na2O, K2O, CoO, Fe2O3, MgO, SiO2, and ZnO); and (4) compounds that reacted preferentially with cubic zirconia (V2O5, P2O5).

  18. Fitting accuracy and fracture resistance of crowns using a hybrid zirconia frame made of both porous and dense zirconia.

    Science.gov (United States)

    Nakamura, Takashi; Sugano, Tsuyoshi; Usami, Hirofumi; Wakabayashi, Kazumichi; Ohnishi, Hiroshi; Sekino, Tohru; Yatani, Hirofumi

    2015-01-01

    The purpose of this study is to evaluate the fitting accuracy and fracture resistance of crowns using a hybrid zirconia frame made of both porous and dense zirconia. Commercial semi-sintered zirconia, sintered dense zirconia and sintered hybrid zirconia were used. Sintered zirconia was milled using the CAD/CAM system, and semi-sintered zirconia was milled and sintered to fabricate molar crown frames. Completed frames were veneered with tooth-colored porcelain. The marginal and internal gaps between frames/crowns and abutments were measured. Each crown specimen was subjected to a fracture test. There were no significant differences in marginal and internal gap among all the frames and crowns. The crown with the hybrid zirconia frame had a 31-35% greater fracture load than that with the commercial or dense zirconia frame (pcrowns with a hybrid zirconia frame have a high fracture resistance.

  19. Synthesis of Ceria Zirconia Oxides using Solvothermal Treatment

    Directory of Open Access Journals (Sweden)

    Machmudah Siti

    2018-01-01

    Full Text Available Ceria oxide (CeO2 is widely used as catalyst with high oxygen storage capacity at low temperature. The addition of zirconia oxide (ZrO2 to CeO2 can enhance oxygen storage capacity as well as thermal stability. In this work, ceria zirconia oxides has been synthesized via a low temperature solvothermal treatment in order to produce ceria zirconia oxides composite with high oxygen storage capacity as electrolyte of solid oxide fuel cells (SOFC. Under solvothermal conditions, solvent may control the direction of crystal growth, morphology, particle size and size distribution, because of the controllability of thermodynamics and transport properties by pressure and temperature. Water, mixed of water and ethanol (70/30 vol/vol, and mixed of water and ethylene glycol (70/30 vol/vol were used as solvent, while Ce(NO33 and ZrO(NO32 with 0.06 M concentration were used as precursor. The experiments were conducted at temperature of 150 °C and pressure for 2 h in a Teflon-lined autoclave of 100 mL volume. The synthesized products were dried at 60 °C for 6 and 12 h and then calcined at 900 °C for 6 h. The particle products were characterized using SEM, XRD, TG/DTA, and Potentiostat. The results showed that the morphology of particles formed were affected by the solvent. Solid plate shaped particles were produced in water, and tend to be pore with the addition of ethylene glycol. The addition of ethanol decreased the size of particles with sphere shaped. The XRD pattern indicated that ceria-zirconia oxides particles are uniformly distributed in the structure to form a homogeneous solid solution. Based on the electrochemical analysis, ceria zirconia oxides produced via solvothermal synthesis had high conductivity ion of 0.5594 S/cm, which is higher than minimum conductivity ion requirement of 0.01 S/cm for SOFC electrolyte. It indicated that ceria zirconia oxides produced via solvothermal synthesis is suitable for SOFC electrolyte.

  20. High-hardness ceramics based on boron carbide fullerite derivatives

    Science.gov (United States)

    Ovsyannikov, D. A.; Popov, M. Yu.; Perfilov, S. A.; Prokhorov, V. M.; Kulnitskiy, B. A.; Perezhogin, I. A.; Blank, V. D.

    2017-02-01

    A new type of ceramics based on the phases of fullerite derivatives and boron carbide B4C is obtained. The material is synthesized at a temperature of 1500 K and a relatively low pressure of 4 GPa; it has a high hardness of 45 GPa and fracture toughness of 15 MPa m1/2.

  1. Cell-based lipid flippase assay employing fluorescent lipid derivatives

    DEFF Research Database (Denmark)

    Jensen, Maria Stumph; Costa, Sara; Günther-Pomorski, Thomas

    2016-01-01

    , studies of individual P4-ATPase family members from fungi, plants, and animals show that P4-ATPases differ in their substrate specificities and mediate transport of a broader range of lipid substrates. Here, we describe an assay based on fluorescent lipid derivatives to monitor and characterize lipid...

  2. Synthesis of waste cooking oil based biodiesel via ferric-manganese promoted molybdenum oxide / zirconia nanoparticle solid acid catalyst: influence of ferric and manganese dopants.

    Science.gov (United States)

    Alhassan, Fatah H; Rashid, Umer; Taufiq-Yap, Yun Hin

    2015-01-01

    The utilization of ferric-manganese promoted molybdenum oxide/zirconia (Fe-Mn- MoO3/ZrO2) (FMMZ) solid acid catalyst for production of biodiesel was demonstrated. FMMZ is produced through impregnation reaction followed by calcination at 600°C for 3 h. The characterization of FMMZ had been done using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), transmission electron microscopy(TEM) and Brunner-Emmett-Teller (BET) surface area measurement. The effect of waste cooking oil methyl esters (WCOME's) yield on the reactions variables such as reaction temperature, catalyst loading, molar ratio of methanol/oil and reusability were also assessed. The catalyst was used to convert the waste cooking oil into corresponding methyl esters (95.6%±0.15) within 5 h at 200℃ reaction temperature, 600 rpm stirring speed, 1:25 molar ratio of oil to alcohol and 4% w/w catalyst loading. The reported catalyst was successfully recycled in six connective experiments without loss in activity. Moreover, the fuel properties of WCOME's were also reported using ASTM D 6751 methods.

  3. FACE RECOGNITION BASED ON LOCAL DERIVATIVE TETRA PATTERN

    Directory of Open Access Journals (Sweden)

    A Geetha

    2017-02-01

    Full Text Available This paper proposes a new face recognition algorithm called local derivative tetra pattern (LDTrP. The new technique LDTrP is used to alleviate the face recognition rate under real-time challenges. Local derivative pattern (LDP is a directional feature extraction method to encode directional pattern features based on local derivative variations. The nth -order LDP is proposed to encode the first (n-1th order local derivative direction variations. The LDP templates extract high-order local information by encoding various distinctive spatial relationships contained in a given local region. The local tetra pattern (LTrP encodes the relationship between the reference pixel and its neighbours by using the first-order derivatives in vertical and horizontal directions. LTrP extracts values which are based on the distribution of edges which are coded using four directions. The LDTrP combines the higher order directional feature from both LDP and LTrP. Experimental results on ORL and JAFFE database show that the performance of LDTrP is consistently better than LBP, LTP and LDP for face identification under various conditions. The performance of the proposed method is measured in terms of recognition rate.

  4. Properties of Formula 127 glass prepared with radioactive zirconia calcine

    International Nuclear Information System (INIS)

    Staples, B.A.; Pavlica, D.A.; Cole, H.S.

    1982-09-01

    Formula 127 glass has been developed to immobilize ICPP zirconia calcine. This glass has been prepared remotely on a laboratory scale basis with actual radioactive zirconia calcine retrieved after ten years of storage from Bin Set 2. The aqueous leachability of the glass produced was investigated and compared through application of the MCC-1, MCC-2 and Soxhlet leach tests with that of Formula 127 glass prepared with simulated calcine. The solid state properties of the glasses prepared with actual and simulated calcines were also measured by electron spectroscopy for chemical analysis (ESCA) and scanning electron microscopy energy dispersive x-ray (SEM-EDX). Based on the application of these leaching tests and analysis techniques the properties measured in this study are similar for 127 glass prepared with either simulated or radioactive calcine. 13 figures, 16 tables

  5. Synthesis of mesoporous zirconia using an amphoteric surfactant

    International Nuclear Information System (INIS)

    Kim, A.Y.; Bruinsma, P.J.; Chen, Y.L.; Liu, J.

    1996-01-01

    An amphoteric surfactant, cocamidopropyl betaine, was used for the synthesis of mesoporous zirconia. The carboxylate functionality of the surfactant permitted strong bonding with soluble zirconium species, while the quaternary ammonium group ensured large headgroup area and high solubility under acidic conditions. An amphoteric co-template [betaine, or (carboxymethyl)trimethylammonium hydroxide] improved uniformity of the hexagonal mesophase. Transmission electron microscopy (TEM) of the as-synthesized zirconium sulfate mesophase indicated hexagonal mesostructure, and low-angle X-ray diffraction (XRD) showed a 41 angstrom primary d-spacing and two higher order reflections of a hexagonal lattice. High surface area zirconia was produced by controlled base treatment of the hexagonal mesophase with sodium hydroxide, followed by calcination. TEM and XRD indicated that the mesostructure was stable to 350 C

  6. Effect of cements on fracture resistance of monolithic zirconia crowns

    Science.gov (United States)

    Nakamura, Keisuke; Mouhat, Mathieu; Nergård, John Magnus; Lægreid, Solveig Jenssen; Kanno, Taro; Milleding, Percy; Örtengren, Ulf

    2016-01-01

    Abstract Objectives The present study investigated the effect of cements on fracture resistance of monolithic zirconia crowns in relation to their compressive strength. Materials and methods Four different cements were tested: zinc phosphate cement (ZPC), glass-ionomer cement (GIC), self-adhesive resin-based cement (SRC) and resin-based cement (RC). RC was used in both dual cure mode (RC-D) and chemical cure mode (RC-C). First, the compressive strength of each cement was tested according to a standard (ISO 9917-1:2004). Second, load-to-failure test was performed to analyze the crown fracture resistance. CAD/CAM-produced monolithic zirconia crowns with a minimal thickness of 0.5 mm were prepared and cemented to dies with each cement. The crown–die samples were loaded until fracture. Results The compressive strength of SRC, RC-D and RC-C was significantly higher than those of ZPC and GIC (p crown between the groups. Conclusion The values achieved in the load-to-failure test suggest that monolithic zirconia crowns with a minimal thickness of 0.5 mm may have good resistance against fracture regardless of types of cements. PMID:27335900

  7. Microtensile bond strength of a resin cement to silica-coated and silanized in-ceram zirconia before and after aging

    NARCIS (Netherlands)

    Valandro, Luiz Felipe; Ozcan, Mutlu; Amaral, Regina; Pereira Leite, Fabiola Pessoa; Bottino, Marco Antonio

    2007-01-01

    Purpose: This study compared the microtensile bond strength of resin-based cement (Panavia F) to silica-coated, silanized, glass-infiltrated high-alumina zirconia (In-Ceram Zirconia) ceramic in dry conditions and after various aging regimens. Materials and Methods: The specimens were placed in 1 of

  8. Outcome of zirconia partial fixed dental prostheses made by predoctoral dental students: A clinical retrospective study after 3 to 7 years of clinical service.

    Science.gov (United States)

    Pihlaja, Juha; Näpänkangas, Ritva; Raustia, Aune

    2016-07-01

    Zirconia has an established role in fixed prosthodontics, especially for single crowns. Whether it is durable enough for fixed dental prostheses (FDPs) in the long term is yet unclear. The purpose of this retrospective study was to evaluate the outcome of FDPs made by predoctoral students after 3 to 7 years of clinical service. A total of 102 patients received 120 zirconia FDPs (range, 3-12 units; mean, 4.5 units) between 2007 and 2010. Materials used were Zirkonzahn Zirconia (Zirkonzahn), NobelProcera Zirconia (Nobel Biocare), and Prettau Zirconia (Zirkonzahn). Veneering porcelain was hand-layered on Zirkonzahn Zirconia (GC Initial Zr; GC Europe) and Nobel Procera Zirconia (VITA VM 9; VITA Zahnfabrik). Prettau Zirconia was monolithic and had no veneering porcelain. Success and survival rates were calculated using Kaplan-Meier survival analysis. Ethics approval was obtained from the Ethical Committee of the Northern Ostrobothnia Hospital District (100/2013). The 76 participants examined (75%) had received 88 zirconia FDPs. The mean follow-up period was 4.9 years (range, 3-7 years). The most common complication was chipping of the veneering porcelain in 13 of 88 FDPs (14.7%). The success rate of the zirconia-based partial FDPs after 4.9 years was 89%, and the survival rate was 100%. The success rate of the zirconia-based partial FDPs after 4.9 years was 89%, and the survival rate was 100%. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  9. A new testing protocol for zirconia dental implants.

    Science.gov (United States)

    Sanon, Clarisse; Chevalier, Jérôme; Douillard, Thierry; Cattani-Lorente, Maria; Scherrer, Susanne S; Gremillard, Laurent

    2015-01-01

    Based on the current lack of standards concerning zirconia dental implants, we aim at developing a protocol to validate their functionality and safety prior their clinical use. The protocol is designed to account for the specific brittle nature of ceramics and the specific behavior of zirconia in terms of phase transformation. Several types of zirconia dental implants with different surface textures (porous, alveolar, rough) were assessed. The implants were first characterized in their as-received state by Scanning Electron Microscopy (SEM), Focused Ion Beam (FIB), X-Ray Diffraction (XRD). Fracture tests following a method adapted from ISO 14801 were conducted to evaluate their initial mechanical properties. Accelerated aging was performed on the implants, and XRD monoclinic content measured directly at their surface instead of using polished samples as in ISO 13356. The implants were then characterized again after aging. Implants with an alveolar surface presented large defects. The protocol shows that such defects compromise the long-term mechanical properties. Implants with a porous surface exhibited sufficient strength but a significant sensitivity to aging. Even if associated to micro cracking clearly observed by FIB, aging did not decrease mechanical strength of the implants. As each dental implant company has its own process, all zirconia implants may behave differently, even if the starting powder is the same. Especially, surface modifications have a large influence on strength and aging resistance, which is not taken into account by the current standards. Protocols adapted from this work could be useful. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  10. Influence of Different Framework Designs on the Fracture Properties of Ceria-Stabilized Tetragonal Zirconia/Alumina-Based All-Ceramic Crowns

    Directory of Open Access Journals (Sweden)

    Tomofumi Sawada

    2016-05-01

    Full Text Available The aim of this study was to evaluate the fracture load and failure mode of all-ceramic crowns with different ceria-stabilized tetragonal zirconia/alumina nanocomposite (Ce-TZP/A framework designs. Four frameworks (anatomical shape: AS, with a buccal or lingual supporting structure: BS and LS, or buccal and lingual supporting structures: BLS were fabricated. All frameworks were veneered with porcelain to fabricate all-ceramic crowns followed by cementation to tooth analogs. The fracture load of each crown either without or with pre-loading (1.2 million cycles, 49 N was measured. The failure mode was classified into partial or complete fracture. Differences were tested for significance (p < 0.05 by a two-way Analysis of Variance (ANOVA, followed by Tukey’s test and by Fisher’s exact test, respectively. Without pre-loading, supporting structures did not influence the fracture load or failure mode. Partial fractures were the most common failure mode. Pre-loading promoted the severity of the failure mode, although the fracture load among the framework designs was not influenced. In the AS group, prefailures were observed during pre-loading, and complete fractures were significantly increased after pre-loading. In contrast, the failure mode of the BLS group remained unchanged, showing only partial fracture even after pre-loading. This Ce-TZP/A framework design, comprised of an anatomical shape with additional buccal and lingual structures, has the potential to reduce the chipping of the veneering porcelain.

  11. Two-body wear comparison of zirconia crown, gold crown, and enamel against zirconia.

    Science.gov (United States)

    Kwon, Min-Seok; Oh, Sang-Yeob; Cho, Sung-Am

    2015-07-01

    Full zirconia crowns have recently been used for dental restorations because of their mechanical properties. However, there is little information about their wear characteristics against enamel, gold, and full zirconia crowns. The purpose of this study was to compare the wear rate of enamel, gold crowns, and zirconia crowns against zirconia blocks using an in vitro wear test. Upper specimens were divided into three groups: 10 enamels (group 1), 10 gold crowns (group 2, Type III gold), and 10 zirconia crowns (group 3, Prettau(®)Zirkon 9H, Zirkonzahn, Italy). Each of these specimens was wear tested against a zirconia block (40×30×3mm(3)) as a lower specimen (30 total zirconia blocks). Each specimen of the groups was abraded against the zirconia block for 600 cycles at 1Hz with 15mm front-to-back movement on an abrading machine. Moreover, the load applied during the abrading test was 50N, and the test was performed in a normal saline emulsion for 10min. Three-dimensional images were taken before and after the test, and the statistical analysis was performed using the Krushal-Wallis test and Mann-Whitney test (p=0.05). The mean volume loss of group 1 was 0.47mm(3), while that of group 2 and group 3 was 0.01mm(3). The wear volume loss of enamels against zirconia was higher than that of gold and zirconia crowns. Moreover, according to this result, zirconia crowns are not recommended for heavy bruxers. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Hydration Structures and Water Chemistry at Zirconia-Water Interfaces

    Science.gov (United States)

    Hou, Binyang; Park, Changyong; Kim, Seunghyun; Kim, Taeho; Kim, Ji Hyun; Kim, Jongjin; Hong, Seungbum; Bahn, Chi Bum

    Zirconia is an important material in numerous applications, such as gas sensors, solid oxide fuel cell electrolytes, and bio-medical materials. It also plays a key role on protecting zirconium alloys in highly corrosive environments found in pressurized water reactors. The degradation of the metal/oxide is primarily due to the interactions of surface oxide with water. Here we study the interactions of zirconia with water in terms of interfacial hydration structures at the 8 mol% yttria-stabilized zirconia (YSZ) surfaces using synchrotron-based X-ray reflectivity techniques. Interfacial hydration structures on three crystallographic orientations were determined with sub-angstrom resolution and compared with each other to identify common features and different surface chemistry effects on the interfacial processes. Meanwhile, zinc injection into the reactor coolant system has been known to be effective in both reducing radioactive wastes and stabilizing crud oxide layers of the metal alloys. We also studied the effect of zinc adsorption on the interfacial hydration structures of YSZs. Our X-ray reflectivity data reveal obvious hydration structure changes at (100) and (111) surfaces, but only minor changes at (110) surface. We further confirmed the detailed element specific adsorption profiles of Zn2+ ions near (110) and (111) surfaces with resonant anomalous X-ray reflectivity measurements.

  13. Modeling Temperature and Pricing Weather Derivatives Based on Temperature

    Directory of Open Access Journals (Sweden)

    Birhan Taştan

    2017-01-01

    Full Text Available This study first proposes a temperature model to calculate the temperature indices upon which temperature-based derivatives are written. The model is designed as a mean-reverting process driven by a Levy process to represent jumps and other features of temperature. Temperature indices are mainly measured as deviations from a base temperature, and, hence, the proposed model includes jumps because they may constitute an important part of this deviation for some locations. The estimated value of a temperature index and its distribution in this model apply an inversion formula to the temperature model. Second, this study develops a pricing process over calculated index values, which returns a customized price for temperature-based derivatives considering that temperature has unique effects on every economic entity. This personalized price is also used to reveal the trading behavior of a hypothesized entity in a temperature-based derivative trade with profit maximization as the objective. Thus, this study presents a new method that does not need to evaluate the risk-aversion behavior of any economic entity.

  14. Bond strength enhancement of zirconia-porcelain interfaces via Nd:YAG laser surface structuring.

    Science.gov (United States)

    Henriques, Bruno; Fabris, Douglas; Souza, Júlio C M; Silva, Filipe S; Carvalho, Óscar; Fredel, Márcio C; Mesquita-Guimarães, Joana

    2018-05-01

    The aim of this study was to evaluate the effect of laser surface structuring on the bond strength of feldspar-based porcelain to zirconia, as compared to conventional sandblasting treatment. Thirty cylindrical zirconia substrates, previously sintered, were divided in three groups according to the type of surface conditioning: 1) sandblasting with 50 µm Al 2 O 3 ; 2) laser structuring (Ø25 µm holes); and 3) laser structuring (Ø50 µm holes). Porcelain was injected onto the zirconia substrates. X-ray diffractometry (XRD) was used to evaluate the influence of the laser treatment on zirconia crystallographic phases. Shear bond strength test was performed. Micrographs using SEM were used to evaluate the zirconia surface after each surface treatment and to evaluate the fracture surface after the shear test. The laser-structured groups presented the highest shear bond strength (65 ± 16 MPa and 65 ± 11 MPa, for the 25 µm and 50 µm holes, respectively). The sandblasting samples presented shear bond strength of 37 ± 16 MPa. XRD analysis showed that there was no phase transformation on the thermally affected surface due to laser action. Microcracks were created at some holes due to the high temperature gradient generated by laser. Laser structuring significantly increased (up to 75%) the shear bond strength of zirconia to veneering porcelain as compared to conventional sandblasting treatment. Therefore, laser structuring arises as a surface conditioning method for producing stronger and long lasting zirconia-porcelain interfaces. Copyright © 2018 Elsevier Ltd. All rights reserved.

  15. Low-complexity topological derivative-based segmentation.

    Science.gov (United States)

    Cho, Choong Sang; Lee, Sangkeun

    2015-02-01

    Topological derivative has been employed for image segmentation and restoration. The topological derivative-based segmentation uses two sparse matrices, and the computational complexity of the segmentation grows up dramatically as the image size increases due to the size of the sparse matrix. Therefore, to provide a fast and accurate segmentation with low complexity, an effective scheme is proposed with keeping the same segmentation performance. To further reduce the computational complexity, the parallel processing structure for the proposed scheme is designed and implemented on graphics processing unit (GPU). In particular, to reduce the computational cost of generating and multiplying sparse matrices that are squared symmetric, the 2D filters consisting of the coefficients at nonborder regions of sparse matrices are defined, and the multiplication is converted into a convolution filtering. In addition, to design a parallel processing for the segmentation with the proposed scheme on a GPU, an image is divided into several blocks and they are processed in parallel. Experimental results show that the proposed scheme for topological derivative-based segmentation reduces the computational complexity ~ 908 times, and the complexity of the proposed scheme is reduced ~ 17 times more from the parallel structure. In particular, the higher efficiency can be obtained from large sized images because the complexity of the proposed scheme does not depend on the image size. Moreover, the proposed scheme can provide almost identical segmentation result with the original sparse matrix-based approach. Therefore, we believe that the proposed scheme can be a useful tool for efficient topological derivative-based segmentation.

  16. Coatings on zirconia for medical applications.

    Science.gov (United States)

    Ferraris, M; Verné, E; Appendino, P; Moisescu, C; Krajewski, A; Ravaglioli, A; Piancastelli, A

    2000-04-01

    In order to combine the mechanical properties of a high-strength inert ceramic (yttria-stabilised zirconia, ZrO2-3%Y2O3, defined as zirconia in the text) with the specific properties of bioactive materials, some zirconia samples were coated by two bioactive phosphosilicate glasses and glass-ceramics: RKKP and AP40. Coatings of about 200-300 microm thickness were prepared by a simple and low-cost firing method. They were characterised by optical and scanning electron microscopy (SEM) and compositional analysis (EDS). The adhesion of the coatings on zirconia was tested by shear tests. Vickers indentations at the coating/zirconia interface were performed in order to observe the crack propagation path. The reactivity of glasses and glass-ceramics coatings towards a simulated body fluid (SBF), having the same ion concentration as that of human plasma, was evaluated and compared to that of the bulk glass and glass-ceramics, by examining the morphology of the reaction layer formed on the surface of the coated zirconia after one month of soaking in the SBF at 37 degrees C.

  17. An overview of monolithic zirconia in dentistry

    Directory of Open Access Journals (Sweden)

    Özlem Malkondu

    2016-07-01

    Full Text Available Zirconia restorations have been used successfully for years in dentistry owing to their biocompatibility and good mechanical properties. Because of their lack of translucency, zirconia cores are generally veneered with porcelain, which makes restorations weaker due to failure of the adhesion between the two materials. In recent years, all-ceramic zirconia restorations have been introduced in the dental sector with the intent to solve this problem. Besides the elimination of chipping, the reduced occlusal space requirement seems to be a clear advantage of monolithic zirconia restorations. However, scientific evidence is needed to recommend this relatively new application for clinical use. This mini-review discusses the current scientific literature on monolithic zirconia restorations. The results of in vitro studies suggested that monolithic zirconia may be the best choice for posterior fixed partial dentures in the presence of high occlusal loads and minimal occlusal restoration space. The results should be supported with much more in vitro and particularly in vivo studies to obtain a final conclusion.

  18. The osseointegration of zirconia dental implants.

    Science.gov (United States)

    Assal, Patrick A

    2013-01-01

    Zirconia is currently extensively used in medicine, especially in orthopedic surgery for various joint replacement appliances. Its outstanding mechanical and chemical properties have made it the "material of choice" for various types of prostheses. Its color in particular makes it a favored material to manufacture dental implants. A literature search through Medline enables one to see zirconia's potential but also to point out and identify its weaknesses. The search shows that zirconia is a biocompatible, osteoconductive material that has the ability to osseointegrate. Its strength of bonding to bone depends on the surface structure of the implant. Although interesting, the studies do not allow for the recommendation of the use of zirconia implants in daily practice. The lack of studies examining the chemical and structural composition of zirconia implants does not allow for a "gold standard" to be established in the implant manufacturing process. Randomized clinical trials (RCT) are urgently needed on surface treatments of zirconia implants intended to achieve the best possible osseointegration.

  19. Thermal characteristics of yttria stabilized zirconia nanolubricants

    Directory of Open Access Journals (Sweden)

    Sakthinathan Ganapathy

    2012-01-01

    Full Text Available The transition from microparticles to nanoparticles can lead to a number of changes in its properties. The objective of this work is to analyze the thermal, tribological properties of yttria stabilized zirconia nanoparticles. Nanosized yttria stabilized zir conia particles were prepared by milling the yttria stabilized zirconia (10 ftm in a planetary ball mill equipped with vials using tungsten carbide balls. After 40 hours milled the yttria stabilized zirconia nanoparticles of sizes ranging from 70-90 nm were obtained. The phase composition and morphologies of the assynthesized particles were characterized by energy dispersive X-ray analysis, scanning electron microscope, transmission electron microscope, thermogravimetric analysis and differential scanning calorimeter, and the images of the same were obtained. From TG-DSC analysis it was confirmed that, the yttria stabilized zirconia nanoparticles were heat stable under different thermal conditions which is due to the addition of yttria to pure zirconia. Due to this property of yttria stabilized zirconia nanoparticles, it can be widely used in high transfer application such as lubricant additives. The heat transfer properties of automotive engine lubricants were determined by utilization of measured thermal conductivity, viscosity index, density, flash point, fire point and pour point revealed that lubricants with additive constituents have a significant effect on the resultant heat transfer characteristics of the lubricants.

  20. Synthesis and Antiproliferative Activity of Thioxoflavones Mannich Base Derivatives.

    Science.gov (United States)

    Li, Wei; Li, Xueli; Liu, Manhui; Wang, Qiuan

    2017-07-01

    Two series of 12 novel thioxoflavones Mannich base derivatives 5a-f and 6a-f were synthesized via Mannich reaction of 4',7-dimethoxy-5-hydroxyflavothione (3) or 3',4',7-trimethoxy-5-hydroxyflavothione (4) with appropriate aliphatic amines or alicyclic amines and formaldehyde. Thioxoflavones 3 and 4 were prepared from 4',7-dimethoxy-5-hydroxyflavone (1) and 3',4',7-trimethoxy-5-hydroxyflavone (2) with Lawesson's reagent, respectively. Their antiproliferative activities in vitro were evaluated on a panel of three human cell lines (HeLa, HCC1954, and SK-OV-3) by CCK-8 assay. The results showed that most of the thioxoflavones and their Mannich base derivatives exhibited potential antiproliferative activities on the tested cancer cell lines, with IC 50 values ranging from 9.16 to 55.50 μM. In particular, thioxoflavone 4 and the thioxoflavone Mannich base derivatives 5a and 5d showed the best antiproliferative activity on all three human cancer cell lines; they are promising candidates worthy of further development. The structures of all synthesized compounds were confirmed by 1 H NMR, 13 C NMR, IR, and MS techniques. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Zirconia versus metal: a preliminary comparative analysis of ceramic veneer behavior.

    Science.gov (United States)

    Augstin-Panadero, Ruben; Fons-Font, Antonio; Roman-Rodriguez, Juan Luis; Granell-Ruiz, Maria; del Rio-Highsmith, Jamie; Sola-Ruiz, Maria Fernanda

    2012-01-01

    Clinical studies have revealed a high rate of fracture for porcelain-veneered zirconia-based restorations that varies between 6% and 15% over a 3- to 5-year period. These are high values compared to the 4% fracture rate shown by conventional metal-ceramic restorations over 10 years. To date, little in vitro research has been carried out on the fracture resistance of the new generation of ceramic crowns. The aims of this study were to develop preliminary research on the mechanical failure behavior of three types of porcelain-veneered crowns with zirconia cores when subjected to static compressive loading and to analyze fracture characteristics using scanning electron microscopy (SEM). Eighty individual full-coverage crowns were studied: 60 crowns with a zirconia core and 20 with a metal core (control). Values obtained in compressive testing were as follows: ZirPress: 1,818.01 N, ZirCAD: 1,773.92 N, Lava: 2,210.95 N, and metal-ceramic (control): 2,310.49 N. SEM analysis revealed that 71.66% of zirconia-based restoration mechanical failures were cohesive, while 100% of mechanical failures for metal-ceramic restorations were adhesive. The mechanical behavior of the porcelain veneering on a zirconia core is more fragile than that on metal-ceramic crowns, and when load forces exerted on these restorations lead to mechanical failure, this will occur in the interior of the porcelain veneering.

  2. Radioisotope power system based on derivative of existing Stirling engine

    International Nuclear Information System (INIS)

    Schock, A.; Or, C.T.; Kumar, V.

    1995-01-01

    In a recent paper, the authors presented the results of a system design study of a 75-watt(c) RSG (Radioisotope Stirling Generator) for possible application to the Pluto Fast Flyby mission. That study was based on a Stirling engine design generated by MTI (Mechanical Technology, Inc.). The MTI design was a derivative of a much larger (13 kwe) engine that they had developed and tested for NASA's LERC. Clearly, such a derivative would be a major extrapolation (downsizing) from what has actually been built and tested. To avoid that, the present paper describes a design for a 75-watt RSG system based on derivatives of a small (11-watt) engine and linear alternator system that has been under development by STC (Stirling Technology Company) for over three years and that has operated successfully for over 15,000 hours as of March 1995. Thus, the STC engines would require much less extrapolation from proven designs. The design employs a heat source consisting of two standard General Purpose Heat Source (GPHS) modules, coupled to four Stirling engines with linear alternators, any three of which could deliver the desired 75-watt(e) output if the fourth should fail. The four engines are coupled to four common radiators with redundant heatpipes for rejecting the engines' waste heat to space. The above engine and radiator redundancies promote system reliability. The paper describes detailed analyses to determine the effect of radiator geometry on system mass and performance, before and after an engine or heatpipe failure

  3. Stabilization of metastable tetragonal zirconia nanocrystallites by surface modification

    DEFF Research Database (Denmark)

    Nielsen, Mette Skovgaard; Almdal, Kristoffer; Lelieveld, A. van

    2011-01-01

    Metastable tetragonal zirconia nanocrystallites were studied in humid air and in water at room temperature (RT). A stabilizing effect of different surfactants on the tetragonal phase was observed. Furthermore, the phase stability of silanized metastable tetragonal zirconia nanocrystallites...

  4. The Effect of Zirconia in Hydroxyapatite on Staphylococcus epidermidis Growth

    Directory of Open Access Journals (Sweden)

    Widowati Siswomihardjo

    2012-01-01

    . Conclusion. The addition of zirconia into hydroxyapatite affected the growth of S. epidermidis. Hydroxyapatite with 20% zirconia proved to be an effective concentration to inhibit the growth of S. epidermidis colony.

  5. Three-Point Bending Tests of Zirconia Core/Veneer Ceramics for Dental Restorations

    Directory of Open Access Journals (Sweden)

    Massimo Marrelli

    2013-01-01

    Full Text Available Introduction. The mechanical strength and the surface hardness of commercially available yttrium-doped zirconia were investigated. Furthermore, a comparative study of eight different ceramic veneers, to be used for the production of two-layered all-ceramic restorative systems, was carried out. Materials and Methods. Four types of zirconia specimens were analyzed, according to a standard ISO procedure (ISO 6872. Besides, two-layered zirconia-veneer specimens were prepared for three-point bending tests. Results. A strong effect of the surface roughness on the mechanical strength of zirconia specimens was observed. Finally, a comparative study of eight commercially available veneering ceramics shows different modes of failure between the selected veneers. Conclusion. The results indicate that close attention should be paid to the preparation of zirconia-based crowns and bridges by CAD/CAM process, because surface roughness has an important effect on the mechanical strength of the material. Finally, the results of the mechanical tests on two-layered specimens represent an important support to the choice of the veneering ceramic.

  6. A review of engineered zirconia surfaces in biomedical applications

    OpenAIRE

    Yin, Ling; Nakanishi, Yoshitaka; Alao, Abdur-Rasheed; Song, Xiao-Fei; Abduo, Jaafar; Zhang, Yu

    2017-01-01

    Zirconia is widely used for load-bearing functional structures in medicine and dentistry. The quality of engineered zirconia surfaces determines not only the fracture and fatigue behaviour but also the low temperature degradation (ageing sensitivity), bacterial colonization and bonding strength of zirconia devices. This paper reviews the current manufacturing techniques for fabrication of zirconia surfaces in biomedical applications, particularly, in tooth and joint replacements, and influenc...

  7. Characterization of combustion synthesized zirconia powder by UV ...

    Indian Academy of Sciences (India)

    Unknown

    Recently, the surface areas of zirconia and sulfated zirconia have been expanded employing surfac- tant template methods (Sudhakar Reddy and Sayari 1996;. Kim et al 1997). The present study describes synthesis of nanocrystalline zirconia using combustion method and its bulk and surface characterization employing ...

  8. Biomolecular modification of zirconia surfaces for enhanced biocompatibility

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Shih-Kuang; Hsu, Hsueh-Chuan [Department of Dental Technology and Materials Science, Central Taiwan University of Science and Technology, Taichung 40601, Taiwan, ROC (China); Ho, Wen-Fu [Department of Chemical and Materials Engineering, National University of Kaohsiung, Taiwan, ROC (China); Yao, Chun-Hsu [Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung 40402, Taiwan, ROC (China); Chang, Pai-Ling [Taoyuan General Hospital, Taoyuan 33004, Taiwan, ROC (China); Wu, Shih-Ching, E-mail: scwu@ctust.edu.tw [Department of Dental Technology and Materials Science, Central Taiwan University of Science and Technology, Taichung 40601, Taiwan, ROC (China)

    2014-12-01

    Yttria-tetragonal zirconia polycrystal (Y-TZP) is a preferred biomaterial due to its good mechanical properties. In order to improve the biocompatibility of zirconia, RGD-peptide derived from extracellular matrix proteins was employed to modify the surface of Y-TZP to promote cell adhesion in this study. The surface of Y-TZP specimens was first modified using a hydrothermal method for different lengths of time. The topographies of modified Y-TZP specimens were analyzed by contact angle, XRD, FTIR, AFM, and FE-SEM. The mechanical properties were evaluated using Vickers hardness and three point bending strength. Then, the RGD-peptide was immobilized on the surface of the Y-TZP by chemical treatment. These RGD-peptide immobilized Y-TZP specimens were characterized by FTIR and AFM, and then were cocultured with MG-63 osteoblast cells for biocompatibility assay. The cell morphology and proliferation were evaluated by SEM, WST-1, and ALP activity assay. The XRD results indicated that the phase transition, from tetragonal phase to monoclinic phase, was increased with a longer incubation time of hydrothermal treatment. However, there were no significant differences in mechanical strengths after RGD-peptide was successfully grafted onto the Y-TZP surface. The SEM images showed that the MG-63 cells appeared polygonal, spindle-shaped, and attached on the RGD-peptide immobilized Y-TZP. The proliferation and cellular activities of MG-63 cells on the RGD-peptide immobilized Y-TZP were better than that on the unmodified Y-TZP. From the above results, the RGD-peptide can be successfully grafted onto the hydrothermal modified Y-TZP surface. The RGD-peptide immobilized Y-TZP can increase cell adhesion, and thus, improve the biocompatibility of Y-TZP. - Highlights: • Covalent bonding between peptide and Y-TZP was proposed. • Stable biomimetic structures produced on the surface of zirconia. • The biocompatibility was improved.

  9. Synthesis, characterization and biological evaluation of tryptamine based benzamide derivatives.

    Science.gov (United States)

    Aftab, Kiran; Aslam, Kinza; Kousar, Shazia; Nadeem, Muhammad Jawad Ul Hasan

    2016-03-01

    Benzamides and tryptamine are biologically significant compounds, therefore, various benzamide analogous of tryptamine have been efficiently synthesized using tryptamine and different benzoyl chlorides, in order to find new biologically active compounds. The resulting products were then characterized by melting point determination, calculation of Rf values and LC-MS techniques. At last, structure activity relationship (SAR) of the synthesized compounds was evaluated against two microbial strains; Bacillus subtilis and Aspergillus niger. All the five prepared products have shown high yield, sharp characterization and significant resistance against the growth of tested microorganism, providing a new range of tryptamine based benzamide derivatives having significant antimicrobial activities.

  10. Microstructure and durability of zirconia thermal barrier coatings

    International Nuclear Information System (INIS)

    Suhr, D.S.; Mitchell, T.E.; Keller, R.J.

    1983-01-01

    Various combinations of plasma-sprayed bond coatings and zirconia ceramic coatings on a nickel-based superalloy substrate were tested by static thermal exposure at 1200 0 C and cyclic thermal exposure to 1000 0 C. The bond coats were based on Ni-Cr-Al alloys with additions of rare earth elements and Si. The ceramic coats were various ZrO 2 -Y 2 O 3 compositions, of which the optimum was found to be ZrO 2 -8.9 wt% Y 2 O 3 . Microstructural analysis showed that resistance to cracking during thermal exposure is strongly related to deleterious phase changes

  11. Phase quantification of mullite-zirconia and zircon commercial powders using PAC and XRD techniques

    Energy Technology Data Exchange (ETDEWEB)

    Rendtorff, Nicolas M.; Conconi, Maria S.; Aglietti, Esteban F. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC: CONICET-CIC) (Argentina); Chain, Cecilia Y.; Pasquevich, Alberto F. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina); Rivas, Patricia C. [CONICET (Argentina); Martinez, Jorge A., E-mail: toto@fisica.unlp.edu.ar; Caracoche, Maria C. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina)

    2010-06-15

    The short range technique of the Perturbed Angular Correlation (PAC) and x-ray diffraction (Rietveld) methods have been employed to determine the phase content in commercial mullite-zirconia and zircon raw materials that are ordinarily used to produce ceramic materials. The PAC technique, which probes zirconium-containing compounds at nanoscopic level, showed that zircon contains crystalline ZrSiO{sub 4} and an important amount of a structurally distorted zircon, which is also observed accompanying monoclinic zirconia in mullite-zirconia. This particular zircon phase was not detected by the long range x-ray diffraction-Rietveld technique. After an annealing treatment, important changes in crystalline contents of the powders allow confirming, by the x-ray diffraction-Rietveld method, the preexistence of this particular zircon phase. This fact must be taken into account when preparing multicomposites based on the present raw materials.

  12. Comparison of light transmittance in different thicknesses of zirconia under various light curing units.

    Science.gov (United States)

    Cekic-Nagas, Isil; Egilmez, Ferhan; Ergun, Gulfem

    2012-05-01

    The objective of this study was to compare the light transmittance of zirconia in different thicknesses using various light curing units. A total of 21 disc-shaped zirconia specimens (5 mm in diameter) in different thicknesses (0.3, 0.5 and 0.8 mm) were prepared. The light transmittance of the specimens under three different light-curing units (quartz tungsten halogen, light-emitting diodes and plasma arc) was compared by using a hand-held radiometer. Statistical significance was determined using two-way ANOVA (α=.05). ANOVA revealed that thickness of zirconia and light curing unit had significant effects on light transmittance (Plight transmittance. Light-emitting diodes light-curing units might be considered as effective as Plasma arc light-curing units or more effective than Quartz-tungsten-halogen light-curing units for polymerization of the resin-based materials.

  13. Leveling and thixotropic characteristics of concentrated zirconia inks for screen-printing

    DEFF Research Database (Denmark)

    Phair, John; Lundberg, Mats; Kaiser, Andreas

    2009-01-01

    Screen-printing is a cost-effective method for the mass manufacture of zirconia-based solid oxide fuel cells (SOFCs) and oxygen separation membranes. The present work outlines an investigation into the leveling, thixotropic, and screen-printing characteristics of concentrated zirconia inks...... of ethyl cellulose (binder) content upon the thixotropic and leveling characteristics of zirconia inks. While the yield stress (τ 0), extent of recovery R(%), and rate of recovery (K) increase with increasing binder content, so did the surface roughness and thickness of the screen-printed films. Increasing...... by a variety of rheological and imaging methods. A combination of viscosity, shear rate jump experiments, creep and recovery analysis, and yield stress measurements were used to assess ink thixotropy. Oscillatory rheometry and scanning electron microscopy/optical microscopy revealed a consistent effect...

  14. Assessment and comparison of retention of zirconia copings luted with different cements onto zirconia and titanium abutments: An in vitro study

    OpenAIRE

    Neelima Sreekumar Menon; G P Surendra Kumar; K R Jnanadev; C L Satish Babu; Shilpa Shetty

    2016-01-01

    Aim: The purpose of this in vitro study was to assess and compare the retention of zirconia copings luted with different luting agents onto zirconia and titanium abutments. Materials and Methods: Titanium and zirconia abutments were torqued at 35 N/cm onto implant analogs. The samples were divided into two groups: Group A consisted of four titanium abutments and 32 zirconia copings and Group B consisted of four zirconia abutments and 32 zirconia copings and four luting agents were used. T...

  15. Fracture behaviour of zirconia FPDs substructures.

    Science.gov (United States)

    Kou, W; Sjögren, G

    2010-04-01

    The purpose of this study was to evaluate the occurrence of superficial flaws after machining and to identify fracture initiation and propagation in three-unit heat-treated machined fixed partial dentures (FPDs) substructures made of hot isostatic pressed (HIPed) yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) after loaded to fracture. Four three-unit HIPed Y-TZP-based FPDs substructures were examined. To evaluate the occurrence of superficial flaws after machining, the surfaces were studied utilizing a fluorescent penetrant method. After static loading to fracture, characteristic fracture features on both mating halves of the fractured specimens were studied using a stereomicroscope and a scanning electron microscope. Grinding grooves were clearly visible on the surfaces of the machined FPDs substructures, but no other flaws could be seen with the fluorescent penetrant method. After loading to fracture, the characteristic fracture features of arrest lines, compression curl, fracture mirror, fracture origin, hackle and twist hackle were detected. These findings indicated that the decisive fracture was initiated at the gingival embrasure of the pontic in association with a grinding groove. Thus, in three-unit heat-treated machined HIPed Y-TZP FPDs substructures, with the shape studied in this study, the gingival embrasure of the pontic seems to be a weak area providing a location for tensile stresses when they are occlusally loaded. In this area, fracture initiation may be located to a grinding groove.

  16. Effect of SiO2 addition in the zirconia stabilization

    International Nuclear Information System (INIS)

    Pessoa, R.C.; Lima, U.R.; Nasar, M.C.; Nasar, R.S.; Yoshida, I.V.P.; Acchar, W.

    2006-01-01

    The aims of this work was investigated the zirconia stabilization with a mixture of resins based on silico nas promoting the Zr O 2 /Si O 2 formation. The powder was heated and characterized by TGA, DTA, FTIR, XRD and SEM/EDS. The results indicated the tetragonal and cubic phase formation stabilized at 1000 deg C/2 h. The increase of calcing temperature promoted decrease of stabilization. The amorphous silica calcined at 1000 deg C induced defects into the zirconia structure and favour the formation of more stable phases. The decrease of stabilization at high temperatures are related to growth of crystallite above of critical value. (author)

  17. Investigation of zircon/zirconia ceramics doped with 239Pu and 238Pu

    International Nuclear Information System (INIS)

    Burakov, B.E.; Anderson, E.B.; Zamoryanskaya, M.V.; Nikolaeva, E.V.; Strykanova, E.E.; Yagovkina, M.A.

    2001-01-01

    Several samples of crystalline double-phase ceramics based on zircon, (Zr,Pu)SiO 4 and zirconia, (Zr,Pu)O 2 , were synthesized by sintering in air, precursors containing approximately 5-6 and 10 wt% 239 Pu, respectively. One sample doped with 5-6 wt% 238-39-40 Pu was also obtained under the same conditions. All ceramic samples were studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and MCC-1 leach test in deionized water at 90 C. Results indicate that even radiation damaged zircon/zirconia ceramics retain high chemical resistance and mechanical durability. (author)

  18. Selective catalytic reduction system and process using a pre-sulfated zirconia binder

    Science.gov (United States)

    Sobolevskiy, Anatoly; Rossin, Joseph A.

    2010-06-29

    A selective catalytic reduction (SCR) process with a palladium catalyst for reducing NOx in a gas, using hydrogen as a reducing agent is provided. The process comprises contacting the gas stream with a catalyst system, the catalyst system comprising (ZrO.sub.2)SO.sub.4, palladium, and a pre-sulfated zirconia binder. The inclusion of a pre-sulfated zirconia binder substantially increases the durability of a Pd-based SCR catalyst system. A system for implementing the disclosed process is further provided.

  19. Tooth-implant-supported posterior fixed dental prostheses with zirconia frameworks: 3-year clinical result.

    Science.gov (United States)

    Beuer, Florian; Sachs, Caroline; Groesser, Julian; Gueth, Jan-Frederik; Stimmelmayr, Michael

    2016-06-01

    This case series compared the clinical survival of tooth-implant-supported (TI-S) and tooth-supported (T-S) three-unit fixed dental prostheses (FDPs) with zirconia frameworks and described the incidence of biological and technical complications. Forty-four patients received 27 TI-S FDPs and 22 T-S FDPs. Twenty-seven titanium screw implants were inserted at the dislodged position of two missing posterior teeth. All implants were provided with customized zirconia abutments. Zirconia frameworks were fabricated by a CAD/CAM system and veneered in powder build-up technique. All restorations were cemented with glass ionomer. Baseline evaluation was performed 2 weeks after cementation with recall examinations performed at 6, 12, 24 and 36 months by calibrated investigators. Survival probabilities according to Kaplan-Meier were calculated. Gingival parameters and bone loss were assessed and statistically evaluated. The mean service time of the FDPs was 35 months (±6). Two technical complications (fracture of veneering porcelain) were observed. One biological complication was recorded. The Kaplan-Meier survival probability was 93.9 % for all types of complications and 100 % related to restorations in service. The type of abutment support (TI-S vs. T-S) had no significant influence on the survival probability (p = 0.412, log rank test). No difference of the gingival parameters was detected between implants and natural teeth. Tooth-implant-supported zirconia-based FDPs showed similar clinical performance compared to tooth-supported zirconia-based FDPs. Within the limitations of this case series, tooth-implant-supported FDPs with zirconia frameworks seem to be a reliable treatment option.

  20. Zirconia doped silicon nitride ceramics

    International Nuclear Information System (INIS)

    Ekstroem, T.; Falk, L.K.L.; Knutson-Wedel, E.M.

    1992-01-01

    This presentation is concerned with the value added to silicon nitride ceramics by doping with smaller amounts of zirconia. The effects which the different sintering additives ZrO 2 , Y 2 O 3 stabilized ZrO 2 , Y 2 O 3 , Al 2 O 3 and AIN have upon densification, α- to β-Si 3 N 4 phase transformation and final microstructure are discussed. Silicon nitride ceramics containing these additives have been formed either by pressureless sintering or by hot isostatic pressing (HIP) at temperatures in the range 1550 to 1775 deg C. The fine scale microstructures of the densified materials, characterized by analytical electron microscopy and X-ray diffractometry, have been related to mechanical properties viz. strength, hardness and indentation fracture toughness. The most pronounced value added by ZrO 2 doping is that a properly adjusted combination of sintering aids makes it possible to substantially reduce the volume fraction of residual intergranular glass through formation of crystalline ZrO 2 (Y 2 O 3 ) solid solutions. This behaviours opens the possibility of developing new silicon nitride ceramics for high temperature applications. 25 refs., 4 figs

  1. Creep of plasma sprayed zirconia

    Science.gov (United States)

    Firestone, R. F.; Logan, W. R.; Adams, J. W.

    1982-01-01

    Specimens of plasma-sprayed zirconia thermal barrier coatings with three different porosities and different initial particle sizes were deformed in compression at initial loads of 1000, 2000, and 3500 psi and temperatures of 1100 C, 1250 C, and 1400 C. The coatings were stabilized with lime, magnesia, and two different concentrations of yttria. Creep began as soon as the load was applied and continued at a constantly decreasing rate until the load was removed. Temperature and stabilization had a pronounced effect on creep rate. The creep rate for 20% Y2O3-80% ZrO2 was 1/3 to 1/2 that of 8% Y2O3-92% ZrO2. Both magnesia and calcia stabilized ZrO2 crept at a rate 5 to 10 times that of the 20% Y2O3 material. A near proportionality between creep rate and applied stress was observed. The rate controlling process appeared to be thermally activated, with an activation energy of approximately 100 cal/gm mole K. Creep deformation was due to cracking and particle sliding.

  2. Microstructural evolution of alumina-zirconia nanocomposites

    International Nuclear Information System (INIS)

    Ojaimi, C.L.; Chinelatto, A.S.A.; Chinelatto, A.L.; Pallone, E.M.J.A.

    2012-01-01

    Ceramic materials have limited use due to their brittleness. The inclusion of nanosized particles in a ceramic matrix, which are called nanocomposites, and ceramic processing control by controlling the grain size and densification can aid in obtaining ceramic products of greater strength and toughness. Studies showed that the zirconia nano inclusions in the matrix of alumina favors an increase in mechanical properties by inhibiting the grain growth of the matrix and not by the mechanism of the transformation toughening phase of zirconia. In this work, the microstructural evolution of alumina nanocomposites containing 15% by volume of nanometric zirconia was studied. From the results it was possible to understand the sintering process of these nanocomposites. (author)

  3. Processing of Alumina-Toughened Zirconia Composites

    Science.gov (United States)

    Bansal, Narottam P.; Choi, Sung R.

    2003-01-01

    Dense and crack-free 10-mol%-yttria-stabilized zirconia (10YSZ)-alumina composites, containing 0 to 30 mol% of alumina, have been fabricated by hot pressing. Release of pressure before onset of cooling was crucial in obtaining crack-free material. Hot pressing at 1600 C resulted in the formation of ZrC by reaction of zirconia with grafoil. However, no such reaction was observed at 1500 C. Cubic zirconia and -alumina were the only phases detected from x-ray diffraction indicating no chemical reaction between the composite constituents during hot pressing. Microstructure of the composites was analyzed by scanning electron microscopy and transmission electron microscopy. Density and elastic modulus of the composites followed the rule-of-mixtures. Addition of alumina to 10YSZ resulted in lighter, stronger, and stiffer composites by decreasing density and increasing strength and elastic modulus.

  4. Anelasticity and strength in zirconia ceramics

    International Nuclear Information System (INIS)

    Matsuzawa, M.; Horibe, S.; Sakai, J.

    2005-01-01

    Non-elastic strain behavior was investigated for several different zirconia ceramics and a possible mechanism for anelasticity was discussed. Anelastic strain was detected in zirconia ceramics irrespective of the crystallographic phase and its productivity depended on the particular kind of dopant additive. It was found that the anelastic properties could be significantly influenced by the level of oxygen vacancy in the matrix, and that the anelastic strain might be produced by a light shift of ionic species. In order to investigate the effect of anelasticity on mechanical properties on zirconia ceramics, the tensile strength was investigated for a wide range of strain rates. The obviously unique strain rate dependence was observed only in the materials having anelastic properties. It was assumed that anelasticity could be efficient at improving the tensile strength. (orig.)

  5. Photoluminescence study on irradiated yttria stabilized zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Halder, R. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Sengupta, Pranesh, E-mail: sengupta@barc.gov.in [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Sudarsan, V. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Ghosh, A. [Glass and Advanced Materials Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Ghosh, A.; Bhukta, A. [Institute of Physics, Bhubaneswar 751005 (India); Sharma, G. [Mechanical Metallurgy Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Samajdar, I. [Dept. of Metall. Engg. and Materials Science, Indian Institute of Technology Bombay, Mumbai 400 076 (India); Dey, G.K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2015-01-15

    Highlights: • YSZ and management of nuclear wastes. • Exposure to radiation environment. • First Photoluminescence data on irradiated YSZ pellets. - Abstract: The structural variations within monoclinic, tetragonal and cubic zirconia pellets with different amounts of yttria doping and its subsequent exposure to various proton, silver ion and gamma irradiation fluxes were investigated using photoluminescence spectroscopy. Upon ion irradiation color centers were produced at doses >10{sup 15} ions/cm{sup 2} resulting in purple coloration. The decrease in photoluminescence intensity was observed for proton irradiated pellets except for tetragonal zirconia (6YSZ: 6 mol% Y{sub 2}O{sub 3} doped ZrO{sub 2}). The anomalous behaviour in case of tetragonal zirconia may result from short range ordering of oxygen vacancies around Zr ions occurring in order to relieve the stress/lattice distortions associated with proton impingement.

  6. A short and long range study of mullite-zirconia-zircon composites

    Energy Technology Data Exchange (ETDEWEB)

    Rendtorff, Nicolas M.; Conconi, Maria S.; Aglietti, Esteban F. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC: CONICET-CIC) (Argentina); Chain, Cecilia Y.; Pasquevich, Alberto F. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina); Rivas, Patricia C. [CONICET (Argentina); Martinez, Jorge A., E-mail: toto@fisica.unlp.edu.ar; Caracoche, Maria C. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina)

    2010-06-15

    In the field of refractory materials, ceramics containing mullite-zirconia are the basis of those most used in the industry of glass and steel. It is known that the addition of zircon improves the behavior of the refractory used in service. Knowing that some mullite-zirconia composites properties as fracture strength and the elastic modulus E are associated with the material microstructure integrity, the eventual thermal decomposition of zircon into zirconia and silica could seriously alter the material elastic properties. In this paper the phase content of a series of mullite-zirconia-zircon (3Al{sub 2}O{sub 3}.2SiO{sub 2}-ZrO{sub 2}-ZrSiO{sub 4}) composites is determined at atomic level via perturbed angular correlations (PAC) and compared with that derived from the long range X-ray diffraction technique. PAC results on the as-prepared materials indicate that all nominal zircon is present and that it involves two types of nanoconfigurations, one of them describing aperiodic regions. The thermomechanical properties already reported for these materials could be related to the crystalline to aperiodic zircon concentrations ratio they exhibit.

  7. A short and long range study of mullite-zirconia-zircon composites

    Science.gov (United States)

    Rendtorff, Nicolás M.; Conconi, Maria S.; Aglietti, Esteban F.; Chain, Cecilia Y.; Pasquevich, Alberto F.; Rivas, Patricia C.; Martínez, Jorge A.; Caracoche, María C.

    2010-06-01

    In the field of refractory materials, ceramics containing mullite-zirconia are the basis of those most used in the industry of glass and steel. It is known that the addition of zircon improves the behavior of the refractory used in service. Knowing that some mullite-zirconia composites properties as fracture strength and the elastic modulus E are associated with the material microstructure integrity, the eventual thermal decomposition of zircon into zirconia and silica could seriously alter the material elastic properties. In this paper the phase content of a series of mullite-zirconia-zircon (3Al2O3.2SiO2-ZrO2-ZrSiO4) composites is determined at atomic level via perturbed angular correlations (PAC) and compared with that derived from the long range X-ray diffraction technique. PAC results on the as-prepared materials indicate that all nominal zircon is present and that it involves two types of nanoconfigurations, one of them describing aperiodic regions. The thermomechanical properties already reported for these materials could be related to the crystalline to aperiodic zircon concentrations ratio they exhibit.

  8. Infrared wire-grid polarizer with sol-gel zirconia grating

    Science.gov (United States)

    Yamada, Itsunari; Ishihara, Yoshiro

    2017-05-01

    The infrared wire-grid polarizer consisting of an Al grating, Si, and sol-gel derived zirconia grating film was fabricated by soft imprint process and Al shadow coating processes. A silicone mold was used because of its low surface energy, flexibility, and capability of transferring submicrosized patterns. As a result, the Al grating with a pitch of 400 nm and a depth of 100 nm was obtained on the zirconia grating film. The fabricated polarizer exhibited a polarization function with the TM transmittance greater than that of the Si substrate in the specific wavelength range of 3.6-8.5 μm, because the zirconia film acted as an antireflection film. The maximum value was 63% at a wavelength of 5.2 μm. This increment of the TM transmission spectrum results in interference within the zirconia film. Also, the extinction ratio exceeded almost 20 dB in the 3-8.8 μm wavelength range.

  9. Chipping Resistance of Graded Zirconia Ceramics for Dental Crowns

    Science.gov (United States)

    Zhang, Y.; Chai, H.; Lee, J.J.-W.; Lawn, B.R.

    2012-01-01

    A serious drawback of veneering porcelains is a pronounced susceptibility to chipping. Glass-infiltrated dense zirconia structures can now be produced with esthetic quality, making them an attractive alternative. In this study, we examined the hypothesis that such infiltrated structures are much more chip-resistant than conventional porcelains, and at least as chip-resistant as non-infiltrated zirconia. A sharp indenter was used to produce chips in flat and anatomically correct glass-infiltrated zirconia crown materials, and critical loads were measured as a function of distance from the specimen edge (flat) or side wall (crown). Control data were obtained on zirconia specimens without infiltration and on crowns veneered with porcelains. The results confirmed that the resistance to chipping in graded zirconia is more than 4 times higher than that of porcelain-veneered zirconia and is at least as high as that of non-veneered zirconia. PMID:22232142

  10. Zirconia femoral head fractures: a clinical and retrieval analysis.

    Science.gov (United States)

    Masonis, John L; Bourne, Robert B; Ries, Michael D; McCalden, Richard W; Salehi, Abraham; Kelman, David C

    2004-10-01

    Zirconia femoral heads provide increased fracture strength, but 343 zirconia head failures have been documented since 2000. Retrieval analysis of 6 fractured heads, 4 suspect heads, 4 control zirconia heads, and 2 failed alumina heads was performed. Zirconia failures have been isolated to heads sintered in a "tunnel" furnace introduced in 1998. The monoclinic composition at the taper surface of fractured and nonfractured heads was significantly elevated (21% to 68%) compared to that of control zirconia heads (less than 5%). Electron microscopy identified circular fracture footprints unique to the zirconia heads produced in the tunnel furnace. Cobalt chrome heads were used in the urgent revision setting due to Morse taper damage. Partial capsulectomy was performed in an effort to reduce future third body wear. Monoclinic phase transformation following implantation remains a potential mechanism of ceramic head failure. We recommend that patients with recalled zirconia heads be advised of a potential fracture risk.

  11. Microscopic derivation of particle-based coarse-grained dynamics

    Science.gov (United States)

    Izvekov, Sergei

    2013-04-01

    In this paper we revisit the derivation of equations of motion for coarse-grained (CG) particles from the microscopic Hamiltonian dynamics of the underlying atomistic system in equilibrium. The derivation is based on the projection operator method and time-convolution equation. We demonstrate that due to the energy exchange between CG and intraparticle phase space coordinates in the microscopic system, the choice of projection operator is not unique, leading to different CG equations of motion that have the form of the nonlinear generalized Langevin equation (GLE). We derive the idempotence properties for the projection operators along the system trajectories and show that these properties result in streaming terms of the respective GLEs that are conservative forces and allow the expression of the non-conservative forces explicitly through thermodynamic averages, which can be measured from the microscopic simulations. The difference between GLEs that are presented herein lies in how the non-conservative forces are partitioned into dissipative and projected contributions. We compute the projected force and analyze conditions under which the projected (stochastic) force is orthogonal to (uncorrelated with) the momenta of CG particles, therefore justifying a transition to a framework of stochastic differential equations. We show that a position- and momentum-independent memory function appears only if the projected force is fully decoupled from the past CG positions and momenta, respectively. In the case of non-vanishing correlations between the projected force and the CG coordinates in past times, we derive explicitly the position- and momentum-dependent memory function in a form of projection onto a space spanned by N-order Hermite polynomials. The expressions presented herein can be used to construct a hierarchy of thermodynamically consistent CG models with momentum-dependent memory functions. They can also be used to design computational schemes for obtaining the

  12. Retention behavior of double-crown attachments with zirconia primary and secondary crowns.

    Science.gov (United States)

    Schwindling, Franz Sebastian; Stober, Thomas; Rustemeier, Rainer; Schmitter, Marc; Rues, Stefan

    2016-05-01

    To investigate whether adequate retention of zirconia conical crown (CC) attachments can be achieved, and to investigate their long-term retention. Sixteen individual zirconia primary crowns were produced with convergence angles of 1° or 2° (eight of each). After determination of the convergence angles of the primary crowns, monolithic zirconia secondary crowns were manufactured. To evaluate the retention behavior of all-zirconia CC, the crowns were fitted with forces from F=12.5-100 N. Force magnitudes during the loosening process (L) were then measured. L/F ratios were recorded and the coefficient of friction (μ0) was calculated. Long-term retention was tested with up to 50,000 cycles of denture integration at a speed of 30 mms(-1) and a fitting force magnitude of 53 N. Even when primary crowns were manufactured with the utmost care, the real convergence angles were greater than the nominal angles of the standardized burs (1° and 2°) by 0.28° (SD 0.11°). Without mechanical aging, mean L/F was 0.632 (SD 0.038) for 1° samples and 0.526 (SD 0.022) for 2° samples, indicative of high retentive forces of up to 63.2% of the fitting forces. When all the test results were used, best-fitting curves gave μ0=0.117 for new samples and μ0=0.126 for samples after 50,000 integration cycles. When the correct milling and sintering parameters are chosen, the retention behavior of zirconia CCs is adequate and stable. This innovative type of attachment is appealing because of the beneficial properties of zirconia and the efficient CAD/CAM-based manufacture. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  13. Surface properties of monolithic zirconia after dental adjustment treatments and in vitro wear simulation.

    Science.gov (United States)

    Preis, Verena; Schmalzbauer, Michael; Bougeard, Dominique; Schneider-Feyrer, Sibylle; Rosentritt, Martin

    2015-01-01

    To investigate the surface properties (roughness, composition, phase transformation) of monolithic zirconia specimens after dental adjustment procedures (grinding, polishing) and wear simulation. Zirconia specimens (Cercon base, Cercon ht, DeguDent, G; n=10/material) were successively sintered, ground, and polished with an intraoral polishing kit in a three-step procedure. Sintered zirconia specimens with high surface roughness served as a reference. For each treatment step, wear simulations with steatite plates (d=10 mm) as antagonists were conducted as well as surface roughness tests (Ra), EDX analysis, and X-ray diffraction (XRD) measurements. SEM pictures were taken, and data were statistically analyzed (one-way ANOVA, post hoc Bonferroni, α=0.05). Grinding significantly (p=0.000) increased the roughness of sintered zirconia up to values of 1.36±0.11 μm (Ra). Polishing significantly (p=0.000) reduced Ra. The lowest roughness value after the final polishing step was 0.20±0.03 μm. Wear testing resulted in a further slight decrease of Ra. After the grinding procedure, SEM pictures showed deep grooves that were progressively smoothed by polishing. The EDX spectra showed that magnesium was transferred from steatite antagonists to zirconia by wear. In the XRD-patterns, monoclinic (m) peaks were observed after grinding and polishing. The maximum intensity ratio between the m (11-1) peak and the tetragonal t (111) peak decreased after the completion of all polishing steps. Wear did not induce phase transformation. Adequate polishing reduced the roughness of ground zirconia. Wear had little influence on roughness and no influence on phase transformation. Careful polishing is recommended to keep surface roughness and phase transformation low. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Effect of incorporating BisGMA resin on the bonding properties of silane and zirconia primers.

    Science.gov (United States)

    Chen, Liang; Shen, Hong; Suh, Byoung In

    2013-11-01

    Some silane primers and some zirconia primers contain extra resins such as bisphenol A glycol dimethacrylate (BisGMA) in their formulations for better wetting. No studies exist on the bonding properties of zirconia and silane primers, which contain extra resins. The purpose of this study was to investigate the effect of incorporating BisGMA resin on the bonding properties of silane and zirconia primers. Silica-base lithium disilicate was etched and treated with BisGMA-incorporated Porcelain Primer, unmodified Porcelain Primer, or resin-containing Kerr Silane. Zirconia ceramic was airborne-particle abraded and treated with BisGMA-incorporated Monobond Plus, unmodified Monobond Plus, or BisGMA-containing ZPrime Plus. After primer treatment and cleaning with ethanol, the contact angles were measured to determine surface change (n=10). Shear bond strength tests were also performed to measure the adhesion strength between resin cements and ceramic surfaces (n=10). Data were statistically analyzed by 1-way ANOVA followed by the Tukey multiple comparison as a post hoc test (significance level .05). The incorporation of BisGMA resin did not significantly influence the bond strength or contact angle of the zirconia primer (P>.05), but it did significantly reduce those of the silane primer (PSilane (22 degrees, 23 MPa) had a similar contact angle and higher bond strength than the control (21 degrees, 18 MPa), but lower than Porcelain Primer (88 degrees, 34 MPa). Resin-containing ZPrime Plus (75 degrees, 29 MPa) had a similar contact angle and higher bond strength than both Monobond Plus (74 degrees, 18 MPa) and the control (15 degrees, 4 MPa). The addition of BisGMA resin significantly inhibited the efficacy of silane-containing porcelain primers but did not affect that of phosphate-containing zirconia primers. Copyright © 2013 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  15. The wear of polished and glazed zirconia against enamel.

    Science.gov (United States)

    Janyavula, Sridhar; Lawson, Nathaniel; Lawson, Nathaniel; Cakir, Deniz; Beck, Preston; Ramp, Lance C; Burgess, John O

    2013-01-01

    The wear of tooth structure opposing anatomically contoured zirconia crowns requires further investigation. The purpose of this in vitro study was to measure the roughness and wear of polished, glazed, and polished then reglazed zirconia against human enamel antagonists and compare the measurements to those of veneering porcelain and natural enamel. Zirconia specimens were divided into polished, glazed, and polished then reglazed groups (n=8). A veneering porcelain (Ceramco3) and enamel were used as controls. The surface roughness of all pretest specimens was measured. Wear testing was performed in the newly designed Alabama wear testing device. The mesiobuccal cusps of extracted molars were standardized and used as antagonists. Three-dimensional (3D) scans of the specimens and antagonists were obtained at baseline and after 200 000 and 400 000 cycles with a profilometer. The baseline scans were superimposed on the posttesting scans to determine volumetric wear. Data were analyzed with a 1-way ANOVA and Tukey Honestly Significant Difference (HSD) post hoc tests (α=.05) Surface roughness ranked in order of least rough to roughest was: polished zirconia, glazed zirconia, polished then reglazed zirconia, veneering porcelain, and enamel. For ceramic, there was no measureable loss on polished zirconia, moderate loss on the surface of enamel, and significant loss on glazed and polished then reglazed zirconia. The highest ceramic wear was exhibited by the veneering ceramic. For enamel antagonists, polished zirconia caused the least wear, and enamel caused moderate wear. Glazed and polished then reglazed zirconia showed significant opposing enamel wear, and veneering porcelain demonstrated the most. Within the limitations of the study, polished zirconia is wear-friendly to the opposing tooth. Glazed zirconia causes more material and antagonist wear than polished zirconia. The surface roughness of the zirconia aided in predicting the wear of the opposing dentition

  16. Raman spectroscopic characterization of ZrO2 and yttrium stabilized zirconias

    DEFF Research Database (Denmark)

    Kjerulf-Jensen, N.; Berg, Rolf W.; Poulsen, Finn Willy

    1996-01-01

    Current literature on the analysis of vibrational spectra of monoclinic, tetragonal and cubic zirconias is reviewed. The selection rules based on simple factor group analysis are not obeyed for the structurally disordered tetragonal and cubic materials. The interpretation is thus not straight...

  17. Fracture and shear bond strength analyses of different dental veneering ceramics to zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Diniz, Alexandre C. [School of Dentistry (DOD), Division of Prosthodontics, Universidade Federal do Rio Grande do Norte -UFRN, 59056-000, Natal (Brazil); Nascimento, Rubens M. [Materials Engineering Department, Universidade Federal do Rio Grande do Norte - UFRN, Natal (Brazil); Souza, Julio C.M. [Centre for Mechanics and Materials Technologies - CT2M, Department of Mechanical Engineering (DEM), Universidade do Minho, Campus Azurém, 4800-058, Guimarães (Portugal); Henriques, Bruno B. [Materials Engineering Department, Universidade Federal do Rio Grande do Norte - UFRN, Natal (Brazil); Centre for Mechanics and Materials Technologies - CT2M, Department of Mechanical Engineering (DEM), Universidade do Minho, Campus Azurém, 4800-058, Guimarães (Portugal); Carreiro, Adriana F.P., E-mail: adrianadafonte@hotmail.com [School of Dentistry (DOD), Division of Prosthodontics, Universidade Federal do Rio Grande do Norte -UFRN, 59056-000, Natal (Brazil)

    2014-05-01

    The purpose of this work was to evaluate the interaction of different layering porcelains with zirconia via shear bond strength test and microscopy. Four different groups of dental veneering porcelains (VM9, Zirkonzanh, Ceramco, IPS) were fused onto forty zirconia-based cylindrical substrates (8 mm in diameter and 12 mm in height) (n = 10), according to the manufacturer's recommendations. Additionally, layered dental porcelain (D-sign, Ivoclar) was fired on ten Ni–Cr cylindrical substrates Shear bond strength tests of the veneering porcelain to zirconia or Ni–Cr were carried out at a crosshead speed of 0.5 mm/min. After the shear bond tests, the interfaces were analyzed by scanning electron microscopy (SEM). The fracture type exhibited by the different systems was also assessed. The results were statistically analyzed by ANOVA at a significant level of p < .05. The shear bond strength values of the porcelain-to-NiCr interfaces (25.3 ± 7.1 MPa) were significantly higher than those recorded for the following porcelain-to-zirconia systems: Zirkonzanh (18.8 ± 1 MPa), Ceramco (18.2 ± 4.7 MPa), and IPS (16 ± 4.5 MPa). However, no significant differences were found in the shear bond strength values between the porcelain-to-NiCr and porcelain (VM9)-to-zirconia (23.2 ± 5.1 MPa) groups (p > .05). All-ceramic interfaces revealed mixed failure type, cohesive in the porcelain and adhesive at the interface. This study demonstrated that all-ceramic systems do not attain yet the same bond strength standards equivalent to metal–ceramic systems. Therefore, despite the esthetic appeal of all-ceramic restorations, the adhesion between the porcelain and zirconia framework is still an issue considering the long term success of the restoration. - Highlights: • This study assessed the shear bond strength of different porcelains to zirconia. • The porcelain Vita VM9 showed a high shear bond strength to zirconia. • The fracture surface of all-ceramic systems revealed

  18. Fracture and shear bond strength analyses of different dental veneering ceramics to zirconia

    International Nuclear Information System (INIS)

    Diniz, Alexandre C.; Nascimento, Rubens M.; Souza, Julio C.M.; Henriques, Bruno B.; Carreiro, Adriana F.P.

    2014-01-01

    The purpose of this work was to evaluate the interaction of different layering porcelains with zirconia via shear bond strength test and microscopy. Four different groups of dental veneering porcelains (VM9, Zirkonzanh, Ceramco, IPS) were fused onto forty zirconia-based cylindrical substrates (8 mm in diameter and 12 mm in height) (n = 10), according to the manufacturer's recommendations. Additionally, layered dental porcelain (D-sign, Ivoclar) was fired on ten Ni–Cr cylindrical substrates Shear bond strength tests of the veneering porcelain to zirconia or Ni–Cr were carried out at a crosshead speed of 0.5 mm/min. After the shear bond tests, the interfaces were analyzed by scanning electron microscopy (SEM). The fracture type exhibited by the different systems was also assessed. The results were statistically analyzed by ANOVA at a significant level of p < .05. The shear bond strength values of the porcelain-to-NiCr interfaces (25.3 ± 7.1 MPa) were significantly higher than those recorded for the following porcelain-to-zirconia systems: Zirkonzanh (18.8 ± 1 MPa), Ceramco (18.2 ± 4.7 MPa), and IPS (16 ± 4.5 MPa). However, no significant differences were found in the shear bond strength values between the porcelain-to-NiCr and porcelain (VM9)-to-zirconia (23.2 ± 5.1 MPa) groups (p > .05). All-ceramic interfaces revealed mixed failure type, cohesive in the porcelain and adhesive at the interface. This study demonstrated that all-ceramic systems do not attain yet the same bond strength standards equivalent to metal–ceramic systems. Therefore, despite the esthetic appeal of all-ceramic restorations, the adhesion between the porcelain and zirconia framework is still an issue considering the long term success of the restoration. - Highlights: • This study assessed the shear bond strength of different porcelains to zirconia. • The porcelain Vita VM9 showed a high shear bond strength to zirconia. • The fracture surface of all-ceramic systems revealed

  19. Fracture Resistance of Zirconia Restorations with a Modified Framework Design

    Directory of Open Access Journals (Sweden)

    sakineh Nikzadjamnani

    2017-12-01

    Full Text Available Objectives: Chipping is one of the concerns related to zirconia crowns. The reasons of chipping have not been completely understood. This in-vitro study aimed to assess the effect of coping design on the fracture resistance of all-ceramic single crowns with zirconia frameworks. Materials and Methods: Two types of zirconia copings were designed (n=12: (1 a standard coping (SC with a 0.5mm uniform thickness and (2 a modified coping (MC consisted of a lingual margin of 1mm thickness and 2mm height connected to a proximal strut of 4mm height and a 0.3mm-wide facial collar. After veneer porcelain firing, the crowns were cemented to metal dies. Afterwards, a static vertical load was applied until failure. The modes of failure were determined. Data were calculated and statistically analyzed by independent samples T-test. P<0.05 was considered statistically significant.Results: The mean and standard deviation (SD of the final fracture resistance equaled to 3519.42±1154.96 N and 3570.01±1224.33 N in SC and MC groups, respectively; the difference was not statistically significant (P=0.9. Also, the mean and SD of the initial fracture resistance equaled to 3345.34±1190.93 N and 3471.52±1228.93 N in SC and MC groups, respectively (P=0.8. Most of the specimens in both groups showed the mixed failure mode. Conclusions: Based on the results, the modified core design may not significantly improve the fracture resistance.

  20. Synthesis and Characterization of Nanostructured Sulfated Zirconias

    Czech Academy of Sciences Publication Activity Database

    Lutecki, M.; Šolcová, Olga; Werner, S.; Breitkopf, C.

    2010-01-01

    Roč. 53, č. 1 (2010), s. 13-20 ISSN 0928-0707 Grant - others:DFG(DE) BR2068/2-1; DFG(DE) BR2068/2-2 Institutional research plan: CEZ:AV0Z40720504 Keywords : sulfated zirconia * template assisted synthesis * porous materials Subject RIV: CA - Inorganic Chemistry Impact factor: 1.525, year: 2010

  1. Mechanical Characterization of Zirconia Ceramic Composite

    Directory of Open Access Journals (Sweden)

    Jin Kelvin Chew Wai

    2018-01-01

    Full Text Available In this day and age, zirconia ceramics are used widely in the medical field as biomaterials for the replacement of damaged body parts. This is because zirconia is one of the closest replacements for bone tissue. However, there were a few cases regarding the failure of zirconia ceramic hip transplants. To overcome this issue, composite materials are being studied as they are able to combine different properties which are not present in a material. This study of Y-TZP/stainless steel 316 composite is carried out with the idea of providing a solution for failure of zirconia implants and also an improvement in biomaterials which will benefit the biomedical world. The study aims to determine the effects on how the increasing of stainless-steel content in the composite will affect the relative density, Vickers hardness, fracture toughness and ageing resistance of the Y-TZP/stainless steel 316 composite. To carry out the research, the composite samples were prepared by mixing the powder of each samples according to their determined content with ethanol. After the powders were mixed, the powders were then pressed, followed by undergoing a Cold Isostatic Press process (CIP and then it underwent sintering at its determined temperature. After sintering, the samples underwent grinding and polishing before being ready for testing. The outcomes of the research showed that as the sintering temperature and the content of stainless-steel increase in the composite, the fracture toughness and ageing resistance improved while the Vickers hardness and relative density decreased.

  2. Peculiarities of structural transformations in zirconia nanocrystals

    Science.gov (United States)

    Vasilevskaya, A.; Almjasheva, O. V.; Gusarov, V. V.

    2016-07-01

    The transitions of metastable tetragonal phase as well as high-temperature tetragonal phase into the low-temperature monoclinic phase upon heating and cooling were thoroughly studied in zirconia nanoparticles. High-temperature X-ray diffraction, thermal analysis and Raman spectroscopy were used to provide the systematic approach to the investigation of zirconia nanoparticles thermal behavior. A phase transformation sequence in the ZrO2-H2O system was determined, and the mechanisms of tetragonal-to-monoclinic transition upon heating and cooling were suggested. Here, the phenomenon was found and described, which was determined as "self-powdering" of nanoparticles occurring during structural transition. This phenomenon was observed by in situ investigation of the evolution of crystalline nanoparticles from amorphous zirconium hydroxide during thermal treatment in air. The tetragonal-to-monoclinic phase transition, induced by cooling from the temperature of equilibrium of tetragonal zirconia (i.e., above 1170 °C), is accompanied by a significant crystallite size decrease (with corresponding 3-4 times decrease of crystallite volume). The experimental results facilitate applications of zirconia nanoparticles to obtain high-performance nanopowders for nanoceramics.

  3. Improved Zirconia Oxygen-Separation Cell

    Science.gov (United States)

    Walsh, John V.; Zwissler, James G.

    1988-01-01

    Cell structure distributes feed gas more evenly for more efficent oxygen production. Multilayer cell structure containing passages, channels, tubes, and pores help distribute pressure evenly over zirconia electrolytic membrane. Resulting more uniform pressure distribution expected to improve efficiency of oxygen production.

  4. Densification of zirconia-hematite nanopowders

    NARCIS (Netherlands)

    Raming, T.P.; Winnubst, Aloysius J.A.; van Zyl, W.E.; Verweij, H.

    2003-01-01

    The densification of dual-phase yttria-doped tetragonal zirconia polycrystals (Y-TZP) and -Fe2O3 (hematite) composite powders is described. Different powder synthesis methods, different forms of dry compaction processes, and two sinter methods (pressureless sintering and sinterforging) were

  5. Mixed-mode reversed-phase and ion-exchange separations of cationic analytes on polybutadiene-coated zirconia.

    Science.gov (United States)

    Hu, Yue; Yang, Xiqin; Carr, Peter W

    2002-08-30

    The retention and selectivity of the chromatographic separation of basic (cationic) analytes on a polybutadiene-coated zirconia (PBD-ZrO2) stationary phase have been studied in greater detail than in previous studies. These separations are strongly influenced by the chemistry of the accessible surface of zirconia. In the presence of buffers which contain hard Lewis bases (e.g., phosphate, fluoride, carboxylic acids) zirconia's surface becomes negatively charged due to adsorption of the buffer anion at the hard Lewis acid sites. Consequently, under most conditions (e.g., neutral pH), cationic analytes undergo both hydrophobic and cation-exchange interactions. This mixed-mode retention process generally leads to greater retention factors for cations relative to those on silica-based reversed phases despite the lower surface areas of the zirconia phase, but, more importantly, adsorption of hard Lewis bases can be used to control the chromatographic selectivity for cationic analytes on these zirconia-based stationary phases. In contrast to our prior work, here we show that when mixed-mode retention takes place, both retention and selectivity are easily adjusted by changing the type of hard Lewis base buffer anion, the type of buffer counter-ion (e.g., sodium, potassium, ammonium), the pH, and the ionic strength of the eluent as well as the type and amount of organic modifier.

  6. Bone tissue response to experimental zirconia implants.

    Science.gov (United States)

    Mihatovic, Ilja; Golubovic, Vladimir; Becker, Jürgen; Schwarz, Frank

    2017-03-01

    This study seeks to assess the bone tissue response at experimental zirconia implants in comparison with titanium implants by means of descriptive histology and histomorphometry in a dog model. Experimental zirconia implants with three different surface roughnesses (Z1  Z2 30.1 % > Z3 28.9 % > Z1 25.1 %, p > 0.05, unpaired t test, respectively). A provisional matrix was evident at all implant surfaces. At 14 days, percentages of BIC increased in all groups (tBIC: Ti 62.1 % > Z3 69.2 %  Z1 42.3 %; nBIC: Z3 58.9 % > Ti 52.2 % > Z2 35.1 % > Z1 32.5 %). Two implants, one of group Z1 and one of group Z2, were lost. At 10 weeks, 13 of 18 zirconia implants were lost, equally distributed between all three surface modifications. The remaining implants revealed increased BIC values (tBIC: Z3 69.5 % > Ti 58.5 % > Z1 49.7 % > Z2 37.1 %; nBIC: Z3 57.2 % > Ti 46.5 % > Z1 32.3 % > Z2 29.3 %). Histomorphometrical analysis showed comparable mean BIC values in all groups at all healing periods without showing statistical differences (p > 0.05, unpaired t test, respectively). The bone tissue response throughout the healing periods was characterized by a constant bone remodeling accompanied by resorption of old bone in favor of new bone formation at both titanium and zirconia implants. Surface roughness had a positive effect on BIC, although not showing statistical significance. Due to the poor survival rate, the experimental zirconia implants investigated may not be suitable for clinical use. Zirconia has been introduced as an alternative biomaterial for dental implants. A profound knowledge about the bone tissue response at zirconia implant surfaces is necessary as it plays an important role for proper osseointegration and long-term stability.

  7. Aqueous-Phase Acetic Acid Ketonization over Monoclinic Zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Qiuxia [Institute for Integrated Catalysis, Pacific Northwest; College; Lopez-Ruiz, Juan A. [Institute for Integrated Catalysis, Pacific Northwest; Cooper, Alan R. [Institute for Integrated Catalysis, Pacific Northwest; Wang, Jian-guo [College; Albrecht, Karl O. [Institute for Integrated Catalysis, Pacific Northwest; Mei, Donghai [Institute for Integrated Catalysis, Pacific Northwest

    2017-12-13

    The effect of aqueous phase on the acetic acid ketonization over monoclinic zirconia has been investigated using first-principles based density functional theory (DFT) calculations. To capture the aqueous phase chemistry over the solid zirconia catalyst surface, the aqueous phase is represented by 111 explicit water molecules with a liquid water density of 0.93 g/cm3 and the monoclinic zirconia is modeled by the most stable surface structure . The dynamic nature of aqueous phase/ interface was studied using ab initio molecular dynamics simulation, indicating that nearly half of the surface Zr sites are occupied by either adsorbed water molecules or hydroxyl groups at 550 K. DFT calculations show that the adsorption process of acetic acid from the liquid water phase to the surface is nearly thermodynamically neutral with a Gibbs free energy of -2.3 kJ/mol although the adsorption strength of acetic acid on the surface in aqueous phase is much stronger than in vapor phase. Therefore it is expected that the adsorption of acetic acid will dramatically affects aqueous phase ketonization reactivity over the monoclinic zirconia catalyst. Using the same ketonization mechanism via the β-keto acid intermediate, we have compared acetic acid ketonization to acetone in both vapor and aqueous phases. Our DFT calculation results show although the rate-determining step of the β-keto acid formation via the C-C coupling is not pronouncedly affected, the presence of liquid water molecules will dramatically affect dehydrogenation and hydrogenation steps via proton transfer mechanism. This work was financially supported by the United States Department of Energy (DOE)’s Bioenergy Technologies Office (BETO) and performed at the Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated for DOE by Battelle Memorial Institute. Computing time and advanced catalyst characterization use was granted by a user proposal at the William R. Wiley

  8. Fracture resistance of CAD-CAM monolithic ceramic and veneered zirconia molar crowns after aging in a mastication simulator.

    Science.gov (United States)

    Bankoğlu Güngör, Merve; Karakoca Nemli, Secil

    2018-03-01

    The demand for ceramic restorations has increased over the past years, and now various machinable materials can be used for chairside computer-aided design and computer aided manufacturing (CAD-CAM) systems. Limited studies of these new materials make it difficult to evaluate their mechanical performance, advantages, and limitations. The purpose of this in vitro study was to investigate the fracture resistance of CAD-CAM monolithic ceramic and veneered zirconia molar crowns after thermomechanical aging. A mandibular first molar tooth was prepared, and 12 different experimental groups were generated (n=10). An aging procedure was performed by subjecting the specimens to 12×10 5 mechanical cycles and 5000 thermocycles. Survival analysis was performed according to the thermomechanical aging. The fracture resistance (load at fracture) of all specimens was evaluated with 1-way analysis of variance after the means had been compared using the Tukey honest significant difference test and Weibull distributions of the experimental groups (α=.05). According to the results, the differences between the fracture resistance of the groups were found to be significant. Restorations in the dual network ceramic crown group fractured catastrophically during thermomechanical aging. In all groups, the highest value was found for monolithic zirconia, followed by monolithic lithium disilicate crowns (Pcrowns made of lithium disilicate derivates and zirconia crowns veneered with lithium disilicate ceramic showed no differences from each other (P>.05). The Weibull modulus (m) ranged from 4.22 to 8.58, and conventionally veneered and overpressed zirconia showed the lowest Weibull modulus values among the tested groups, indicating greater variation of the data. The highest fracture resistance was observed for yttria-stabilized zirconia crowns, followed by lithium disilicate derivates. Veneered zirconia restorations generally showed lower resistance than these ceramics. The dual network

  9. INSURANCE CONTRACTS BASED ON INDICES, A STEP TOWARDS WEATHER DERIVATIVES

    Directory of Open Access Journals (Sweden)

    Boton#537; Horia-Mircea

    2012-07-01

    Full Text Available The aim of this paper is to analyze the methodology of structuring an index based insurance contract. The weather has always been the biggest risk factor in agriculture, affecting all aspects of the economic sectors. In the developed countries of the world, there is a significant number of rain-dependent farmers. To gain insight into potential growth of weather markets in developed countries, we are going to analyze the case of India. In 2003, Basix microfinance company in Hyderabad and ICICI Lombard insurance company in Mumbai have launched a pilot weather insurance, which had as basic index phenomena for Mahahbubnagar district of Andhra Pradesh. Further detail can be found in the full-paper. In the paper we will enumerate the appropriate steps in the determining the necessity for the use of index based insurances. The appropriate stages are making a comparison between index based insurances and traditional insurances, and optimizing the use of weather indices in insurance contracts. In order for the contracts to be successful , the recommended steps are : developing a product based in an index, and after the we need to plan and implement the contract. In planning the implementation it is needed that we: identify the risks and areas where they manifest, then identify the best distribution channels; after this we can develop a prototype of the contract. The next step would the testing of the negotiability of the contract, then the contract is opened to be finalized. After this the index based insurance contract can be introduced to the market, but the program needs monitoring in order to insure its successfulness. In order for the market and contract to grow the necessary step are: having access to the necessary meteorological data, determine the optimal way of integrating the contract in the existing economical context, technical feasibility, property rights and the legal framework. In the end, the aim is to familiarize the literacy field and

  10. Radar-Derived Quantitative Precipitation Estimation Based on Precipitation Classification

    Directory of Open Access Journals (Sweden)

    Lili Yang

    2016-01-01

    Full Text Available A method for improving radar-derived quantitative precipitation estimation is proposed. Tropical vertical profiles of reflectivity (VPRs are first determined from multiple VPRs. Upon identifying a tropical VPR, the event can be further classified as either tropical-stratiform or tropical-convective rainfall by a fuzzy logic (FL algorithm. Based on the precipitation-type fields, the reflectivity values are converted into rainfall rate using a Z-R relationship. In order to evaluate the performance of this rainfall classification scheme, three experiments were conducted using three months of data and two study cases. In Experiment I, the Weather Surveillance Radar-1988 Doppler (WSR-88D default Z-R relationship was applied. In Experiment II, the precipitation regime was separated into convective and stratiform rainfall using the FL algorithm, and corresponding Z-R relationships were used. In Experiment III, the precipitation regime was separated into convective, stratiform, and tropical rainfall, and the corresponding Z-R relationships were applied. The results show that the rainfall rates obtained from all three experiments match closely with the gauge observations, although Experiment II could solve the underestimation, when compared to Experiment I. Experiment III significantly reduced this underestimation and generated the most accurate radar estimates of rain rate among the three experiments.

  11. A Derivative Based Estimator for Semiparametric Index Models

    NARCIS (Netherlands)

    Donkers, A.C.D.; Schafgans, M.

    2003-01-01

    This paper proposes a semiparametric estimator for single- and multiple index models.It provides an extension of the average derivative estimator to the multiple index model setting.The estimator uses the average of the outer product of derivatives and is shown to be root-N consistent and

  12. Design of photocontrolled biomolecules based on azobenzene derivatives

    Science.gov (United States)

    Zatsepin, T. S.; Abrosimova, L. A.; Monakhova, M. V.; Thi Hien, Le; Pingoud, A.; Kubareva, E. A.; Oretskaya, T. S.

    2013-10-01

    This review focuses on methods of designing photocontrolled proteins and nucleic acids. Data on preparation and modification of proteins and nucleic acids with azobenzene derivatives are summarized. Examples of using photoswitchable proteins, their substrates, inhibitors and ligands containing azobenzene, as well as azobenzene derivatives of nucleic acids, for design of nanomachines are considered. The bibliography includes 122 references.

  13. Direct inkjet printing of dental prostheses made of zirconia.

    Science.gov (United States)

    Ebert, J; Ozkol, E; Zeichner, A; Uibel, K; Weiss, O; Koops, U; Telle, R; Fischer, H

    2009-07-01

    CAD/CAM milling systems provide a rapid and individual method for the manufacturing of zirconia dental restorations. However, the disadvantages of these systems include limited accuracy, possible introduction of microscopic cracks, and a waste of material due to the principle of the 'subtractive process'. The hypothesis of this study was that these issues can be overcome by a novel generative manufacturing technique, direct inkjet printing. A tailored zirconia-based ceramic suspension with 27 vol% solid content was synthesized. The suspension was printed on a conventional, but modified, drop-on-demand inkjet printer. A cleaning unit and a drying device allowed for the build-up of dense components of the size of a posterior crown. A characteristic strength of 763 MPa and a mean fracture toughness of 6.7 MPam(0.5) were determined on 3D-printed and subsequently sintered specimens. The novel technique has great potential to produce, cost-efficiently, all-ceramic dental restorations at high accuracy and with a minimum of materials consumption.

  14. Vapour phase dehydration of glycerol to acrolein over tungstated zirconia catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Rao Ginjupalli, Srinivasa; Mugawar, Sowmya; Rajan, Pethan N.; Kumar Balla, Putra; Chary Komandur, V.R., E-mail: kvrchary@iict.res.in

    2014-08-01

    Tetragonal (TZ) and monoclinic (MZ) polymorphs of zirconia supports were synthesised by sol–gel method followed by variation of the calcination temperature. Tungstated (10 wt% WO{sub 3}) supported on the zirconia polymorphs were prepared by impregnation method by using ammonium metatungstate precursor. The physico-chemical properties of the calcined catalysts were characterised by X-ray diffraction, UV–vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area and pore size distribution measurements to gain insight into the effect of morphology of the catalyst textural properties, and structure. The surface acidic properties have been determined by NH{sub 3} TPD method and also with FT-IR spectra of pyridine adsorption. Vapour phase dehydration of glycerol to acrolein was employed to investigate the catalytic functionalities. Glycerol conversion and acrolein selectivity was mainly dependent on the fraction of moderate acid sites with majority of them are due to Brønsted acidic sites. Monoclinic zirconia based catalysts have shown the highest activity and acrolein selectivity compared to the corresponding tetragonal zirconia catalysts.

  15. Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics.

    Science.gov (United States)

    Yoon, Hyung-In; Yeo, In-Sung; Yi, Yang-Jin; Kim, Sung-Hun; Lee, Jai-Bong; Han, Jung-Suk

    2015-01-01

    The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics. The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed. The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p ceramic substances into the zirconia surface. A glass-ceramic based connector is significantly more favorable to core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.

  16. An Harmonic Smile Resulted from the Use of Ceramic Prosthesis with Zirconia Structure: A Case Report

    Science.gov (United States)

    Tavarez, Rudys Rodolfo de Jesus; Goncalves, Leticia Machado; Dias, Ana Paula; Dias, Anna Claudia Pereira; Malheiros, Adriana Santos; Silva, Alice Carvalho; Bandeca, Matheus Coelho

    2014-01-01

    The rehabilitation of patients requiring an esthetic smile demands a multidisciplinary approach. This clinical report describes a treatment plan for recovery aesthetics’ smile of anterior teeth using ceramic prosthesis with zirconia structure. Initially, a review of aesthetic parameters, diagnostic waxing, mock-up and provisional restorations was performed. A contextual assessment of aesthetic, proportion and shape of teeth was done to recreate a natural looking for teeth in consonance with the smile line. Subsequently, based on these parameters, fixed prostheses of the upper anterior teeth using ceramic restorations with zirconia infrastructures were performed. The use of ceramic restorations with zirconia structures associated with a careful treatment plan allows the professional to integrate esthetic and function for satisfactory clinical results. How to cite the article: Tavarez RR, Gonçalves LM, Dias AP, Dias AC, Malheiros AS, Silva AC, Bandeca MC. An harmonic smile resulted from the use of ceramic prosthesis with zirconia structure: A case report. J Int Oral Health 2014;6(3):90-2. PMID:25083040

  17. Cutting efficiency of diamond burs operated with electric high-speed dental handpiece on zirconia.

    Science.gov (United States)

    Nakamura, Keisuke; Katsuda, Yusuke; Ankyu, Shuhei; Harada, Akio; Tenkumo, Taichi; Kanno, Taro; Niwano, Yoshimi; Egusa, Hiroshi; Milleding, Percy; Örtengren, Ulf

    2015-08-28

    Zirconia-based dental restorations are becoming used more commonly. However, limited attention has been given to the difficulties experienced, concerning cutting, in removing the restorations when needed. The aim of the present study was to compare the cutting efficiency of diamond burs, operated using an electric high-speed dental handpiece, on zirconia (Zir) with those on lithium disilicate glass-ceramic (LD) and leucite glass-ceramic (L). In addition, evaluation of the cutting efficiency of diamond burs on Zir of different thicknesses was performed. Specimens of Zir were prepared with thicknesses of 0.5, 1.0, 2.0, and 4.0 mm, and specimens of LD and L were prepared with a thickness of 1.0 mm. Cutting tests were performed using diamond burs with super coarse (SC) and coarse (C) grains. The handpiece was operated at 150,000 rpm with a cutting force of 0.9 N. The results demonstrated that cutting of Zir took about 1.5- and 7-fold longer than cutting of LD and L, respectively. The SC grains showed significantly higher cutting efficiency on Zir than the C grains. However, when the thickness of Zir increased, the cutting depth was significantly decreased. As it is suggested that cutting of zirconia is time consuming, this should be taken into consideration in advance when working with zirconia restorations. © 2015 Eur J Oral Sci.

  18. Vapour phase dehydration of glycerol to acrolein over tungstated zirconia catalysts

    Science.gov (United States)

    Rao Ginjupalli, Srinivasa; Mugawar, Sowmya; Rajan N., Pethan; Kumar Balla, Putra; Chary Komandur, V. R.

    2014-08-01

    Tetragonal (TZ) and monoclinic (MZ) polymorphs of zirconia supports were synthesised by sol-gel method followed by variation of the calcination temperature. Tungstated (10 wt% WO3) supported on the zirconia polymorphs were prepared by impregnation method by using ammonium metatungstate precursor. The physico-chemical properties of the calcined catalysts were characterised by X-ray diffraction, UV-vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area and pore size distribution measurements to gain insight into the effect of morphology of the catalyst textural properties, and structure. The surface acidic properties have been determined by NH3 TPD method and also with FT-IR spectra of pyridine adsorption. Vapour phase dehydration of glycerol to acrolein was employed to investigate the catalytic functionalities. Glycerol conversion and acrolein selectivity was mainly dependent on the fraction of moderate acid sites with majority of them are due to Brønsted acidic sites. Monoclinic zirconia based catalysts have shown the highest activity and acrolein selectivity compared to the corresponding tetragonal zirconia catalysts.

  19. Vapour phase dehydration of glycerol to acrolein over tungstated zirconia catalysts

    International Nuclear Information System (INIS)

    Rao Ginjupalli, Srinivasa; Mugawar, Sowmya; Rajan, Pethan N.; Kumar Balla, Putra; Chary Komandur, V.R.

    2014-01-01

    Tetragonal (TZ) and monoclinic (MZ) polymorphs of zirconia supports were synthesised by sol–gel method followed by variation of the calcination temperature. Tungstated (10 wt% WO 3 ) supported on the zirconia polymorphs were prepared by impregnation method by using ammonium metatungstate precursor. The physico-chemical properties of the calcined catalysts were characterised by X-ray diffraction, UV–vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area and pore size distribution measurements to gain insight into the effect of morphology of the catalyst textural properties, and structure. The surface acidic properties have been determined by NH 3 TPD method and also with FT-IR spectra of pyridine adsorption. Vapour phase dehydration of glycerol to acrolein was employed to investigate the catalytic functionalities. Glycerol conversion and acrolein selectivity was mainly dependent on the fraction of moderate acid sites with majority of them are due to Brønsted acidic sites. Monoclinic zirconia based catalysts have shown the highest activity and acrolein selectivity compared to the corresponding tetragonal zirconia catalysts.

  20. Clinical Evaluation and Patient Satisfaction of Single Zirconia-Based and High-Noble Alloy Porcelain-Fused-to-Metal Crowns in the Esthetic Area: A Retrospective Cohort Study.

    Science.gov (United States)

    Shi, Jun-Yu; Li, Xin; Ni, Jie; Zhu, Zi-Yuan

    2016-10-01

    The aim of this study was to assess clinical survival, complications, and patient satisfaction with single zirconia-based crowns (ZC) or high-noble alloy PFM crowns (HC) in esthetic areas. The study was a retrospective cohort study with up to 3.8 years follow-up (mean 2.5 years). Patients who met the inclusion criteria were reviewed. Survival rates, complications, satisfaction rates (color and form), and overall satisfaction (visual analogue scale, VAS) were evaluated by follow-up examination. Chi-square test (survival, complication, and satisfaction rate) and unpaired t-test (overall satisfaction: VAS) were used to test the difference between the ZC and HC groups. Survival rates and complications were assessed both at subject-level (patient as statistical unit) and at tooth-level (tooth as statistical unit). One hundred and thirteen patients met the inclusion criteria; 95 patients (ZC: 45, HC: 50) with 132 crowns (ZC: 61, HC: 71) were enrolled in the study. The overall survival rate was 93.3% for ZC crowns and 96.0% for HC crowns at subject-level and 93.4% for ZC crowns and 97.2% for HC crowns at tooth-level (p = 0.56 and 0.30, respectively). Veneer chipping was the most frequently seen complication. One HC crown lost retention because of poor cementation. One patient in the ZC group showed progression of periodontal disease. No significant difference of complications was found between the two groups at subject-level and tooth-level (p = 0.37 and 0.34, respectively). The overall satisfaction (VAS) was 8.18 for ZC crowns and 8.46 for HC crowns (p = 0.34). The results of the study showed that a high survival rate could be achieved in both ZC and HC groups. Chipping of the veneering porcelain was the most frequently seen event that led to short-term (less than 3 years) failure and complications. The patients' rating of ZC crowns was not superior to HC crowns. Well-designed studies with high evidence level and large sample size are still needed to further explore the

  1. Stiffness, strength, and failure modes of implant-supported monolithic lithium disilicate crowns: influence of titanium and zirconia abutments.

    Science.gov (United States)

    Joda, Tim; Bürki, Alexander; Bethge, Stefan; Brägger, Urs; Zysset, Philippe

    2015-01-01

    The objective of this study was to evaluate stiffness, strength, and failure modes of monolithic crowns produced using computer-aided design/computer-assisted manufacture, which are connected to diverse titanium and zirconia abutments on an implant system with tapered, internal connections. Twenty monolithic lithium disilicate (LS2) crowns were constructed and loaded on bone level-type implants in a universal testing machine under quasistatic conditions according to DIN ISO 14801. Comparative analysis included a 2 × 2 format: prefabricated titanium abutments using proprietary bonding bases (group A) vs nonproprietary bonding bases (group B), and customized zirconia abutments using proprietary Straumann CARES (group C) vs nonproprietary Astra Atlantis (group D) material. Stiffness and strength were assessed and calculated statistically with the Wilcoxon rank sum test. Cross-sections of each tested group were inspected microscopically. Loaded LS2 crowns, implants, and abutment screws in all tested specimens (groups A, B, C, and D) did not show any visible fractures. For an analysis of titanium abutments (groups A and B), stiffness and strength showed equally high stability. In contrast, proprietary and nonproprietary customized zirconia abutments exhibited statistically significant differences with a mean strength of 366 N (Astra) and 541 N (CARES) (P zirconia abutments (groups C and D) below the implant shoulder. Depending on the abutment design, prefabricated titanium abutment and proprietary customized zirconia implant-abutment connections in conjunction with monolithic LS2 crowns had the best results in this laboratory investigation.

  2. Multilayered thermal insulation formed of zirconia bonded layers of zirconia fibers and metal oxide fibers and method for making same

    Science.gov (United States)

    Wrenn, Jr., George E.; Holcombe, Jr., Cressie E.

    1988-01-01

    A multilayered thermal insulating composite is formed of a first layer of zirconia-bonded zirconia fibers for utilization near the hot phase or surface of a furnace or the like. A second layer of zirconia-bonded metal oxide fibers is attached to the zirconia fiber layer by a transition layer formed of intermingled zirconia fibers and metal oxide fibers. The thermal insulation is fabricated by vacuum molding with the layers being sequentially applied from aqueous solutions containing the fibers to a configured mandrel. A portion of the solution containing the fibers forming the first layer is intermixed with the solution containing the fibers of the second layer for forming the layer of mixed fibers. The two layers of fibers joined together by the transition layer are saturated with a solution of zirconium oxynitrate which provides a zirconia matrix for the composite when the fibers are sintered together at their nexi.

  3. An in vitro evaluation of the zirconia surface treatment by mesoporous zirconia coating on its bonding to resin cement.

    Science.gov (United States)

    Zhang, Yanli; Sun, Ting; Liu, Ruoyu; Feng, Xiaoli; Chen, Aijie; Shao, Longquan

    2014-01-01

    The effect of zirconia surface treatment by mesoporous zirconia coating on the microtensile bond strength (MTBS) between zirconia and resin cement was investigated in this work. 160 zirconia specimens were prepared and divided into four groups according to surface treatments: (1) airborne-particle-abrasion treatment (APA); (2) glass infiltration and hydrofluoric acid treatment (GI+HF); (3) mesoporous zirconia coating (MZ); and (4) no treatment (C). The as-prepared zirconia specimens were bonded using Panavia F2.0 and RelyX Unicem. The MTBS values were tested using a universal testing machine, and data were analyzed using ANOVA and SNK methods (a=0.05). The MTBS values obtained after GI+HF and MZ treatments were significantly higher than those obtained after APA and C treatments (Psurface treatments using GI+HF and MZ yield higher bond strength than those using APA or C, regardless of the resin cements.

  4. Overview of zirconia with respect to gas turbine applications

    Science.gov (United States)

    Cawley, J. D.

    1984-01-01

    Phase relationships and the mechanical properties of zirconia are examined as well as the thermal conductivity, deformation, diffusion, and chemical reactivity of this refractory material. Observations from the literature particular to plasma-sprayed material and implications for gas turbine engine applications are discussed. The literature review indicates that Mg-PSZ (partially stabilized zirconia) and Ca-PSZ are unsuitable for advanced gas turbine applications; a thorough characterization of the microstructure of plasma-sprayed zirconia is needed. Transformation-toughened zirconia may be suitable for use in monolithic components.

  5. Comparative evaluation of shear bond strength of zirconia restorations cleansed various cleansing protocols bonded with two different resin cements: An In vitro study

    Directory of Open Access Journals (Sweden)

    Sriram Sankar

    2017-01-01

    Full Text Available Context: Yttria partially stabilized tetragonal zirconia polycrystalline restorations have gained widespread use because of its enhanced strength and esthetics. During the try-in process, zirconia is likely to be contaminated with saliva. This contamination leads to a clear weakening of the bond between restorative material and cement. For this reason, zirconia surface should be cleaned before cementation. Hence, the purpose of this study is to compare the shear bond strength of zirconia restorations cleansed with various surface cleansing protocols bonded with two different resin cements. Materials and Methods: Eighty samples of zirconia discs were prepared in the dimensions 2.5 mm diameter and 4.5 mm thickness. They were divided into two groups of each forty samples based on luting cement used. Each group was further subdivided into four subgroups of each (n = 10: Group 1: uncontaminated zirconia blocks, Group 2: saliva-contaminated zirconia blocks and cleaned only with distilled water, Group 3: saliva-contaminated zirconia blocks treated with Ivoclean, and Group 4: saliva-contaminated zirconia blocks were air abraded. Eighty human maxillary premolars were then sectioned to expose dentin and were mounted on an acrylic block. A jig was fabricated to bond zirconia with the tooth using two self-adhesive resin cements. The samples were subjected to shear bond strength testing. The data were analyzed using one-way analysis of variance and Tukey's honest significance difference test with a level of significance set at p < 0.05. Results: The mean shear bond strength values of Group 1 and 2 - subgroup B are 10.3 ± 0.4 and 9.80 ± 0.7 (saliva-contaminated zirconia, cleansed with distilled water only, respectively, were lowest among all test subgroups and were significantly less than mean values of subgroup C, Group 1 - 20.45 ± 0.6 and Group 2 - 20.75 ± 0.4 (Ivoclean group and subgroup D, Group 1 - 20.90 ± 0.3 and Group 2 - 20.60 ± 0.5 (air

  6. Phase field modeling of tetragonal to monoclinic phase transformation in zirconia

    Science.gov (United States)

    Mamivand, Mahmood

    Zirconia based ceramics are strong, hard, inert, and smooth, with low thermal conductivity and good biocompatibility. Such properties made zirconia ceramics an ideal material for different applications form thermal barrier coatings (TBCs) to biomedicine applications like femoral implants and dental bridges. However, this unusual versatility of excellent properties would be mediated by the metastable tetragonal (or cubic) transformation to the stable monoclinic phase after a certain exposure at service temperatures. This transformation from tetragonal to monoclinic, known as LTD (low temperature degradation) in biomedical application, proceeds by propagation of martensite, which corresponds to transformation twinning. As such, tetragonal to monoclinic transformation is highly sensitive to mechanical and chemomechanical stresses. It is known in fact that this transformation is the source of the fracture toughening in stabilized zirconia as it occurs at the stress concentration regions ahead of the crack tip. This dissertation is an attempt to provide a kinetic-based model for tetragonal to monoclinic transformation in zirconia. We used the phase field technique to capture the temporal and spatial evolution of monoclinic phase. In addition to morphological patterns, we were able to calculate the developed internal stresses during tetragonal to monoclinic transformation. The model was started form the two dimensional single crystal then was expanded to the two dimensional polycrystalline and finally to the three dimensional single crystal. The model is able to predict the most physical properties associated with tetragonal to monoclinic transformation in zirconia including: morphological patterns, transformation toughening, shape memory effect, pseudoelasticity, surface uplift, and variants impingement. The model was benched marked with several experimental works. The good agreements between simulation results and experimental data, make the model a reliable tool for

  7. Antagonist wear of monolithic zirconia crowns after 2 years.

    Science.gov (United States)

    Lohbauer, Ulrich; Reich, Sven

    2017-05-01

    The aim of this study was to evaluate the amount of wear on the antagonist occlusal surfaces of clinically placed monolithic zirconia premolar and molar crowns (LAVA Plus, 3M ESPE). Fourteen in situ monolithic zirconia crowns and their opposing antagonists (n = 26) are the subject of an ongoing clinical trial and have been clinically examined at baseline and after 24 months. Silicone impressions were taken and epoxy replicas produced for qualitative SEM analysis and quantitative analysis using optical profilometry. Based on the baseline replicas, the follow-up situation has been scanned and digitally matched with the initial topography in order to calculate the mean volume loss (in mm 3 ) as well as the mean maximum vertical loss (in mm) after 2 years in service. The mean volume loss for enamel antagonist contacts (n = 7) was measured to 0.361 mm 3 and the mean of the maximum vertical loss to 0.204 mm. The mean volume loss for pure ceramic contacts (n = 10) was measured to 0.333 mm 3 and the mean of the maximum vertical loss to 0.145 mm. The wear rates on enamel contacts were not significantly different from those measured on ceramic antagonists. Based on the limitations of this study, it can be concluded for the monolithic zirconia material LAVA Plus that the measured wear rates are in consensus with other in vivo studies on ceramic restorations. Further, that no significant difference was found between natural enamel antagonists and ceramic restorations as antagonists. The monolithic zirconia restorations do not seem to be affected by wear within the first 2 years. The monolithic zirconia crowns (LAVA Plus) show acceptable antagonist wear rates after 2 years in situ, regardless of natural enamel or ceramics as antagonist materials.

  8. The effect of graded glass-zirconia structure on the bond between core and veneer in layered zirconia restorations.

    Science.gov (United States)

    Liu, Ruoyu; Sun, Ting; Zhang, Yanli; Zhang, Yaokun; Jiang, Danyu; Shao, Longquan

    2015-06-01

    The aim of this study was to test the hypothesis that a graded glass-zirconia structure can strengthen the core-veneer bond in layered zirconia materials. A graded glass-zirconia structure was fabricated by infiltrating glass compositions developed in our laboratory into a presintered yttria tetrahedral zirconia polycrystal (Y-TZP) substrate by the action of capillary forces. The wettability of the infiltrated glass and Y-TZP substrate was investigated by the sessile drop technique. The microstructures of the graded glass-zirconia structure were examined by scanning electron microscopy (SEM). The phase structure characterization in the graded glass-zirconia structure were identified by X-ray diffraction (XRD) analysis. The elastic modulus and hardness of the graded glass-zirconia structure were evaluated from nanoindentations. Further, the shear bond strength (SBS) of the graded glass-zirconia structure and veneering porcelain was also evaluated. SEM images confirmed the formation of the graded glass-zirconia structure. Glass frits wet the Y-TZP substrate at 1200 °C with a contact angle of 43.2°. Only a small amount of t-m transformation was observed in as-infiltrated Y-TZP specimens. Nanoindentation studies of the glass-zirconia graded structure showed that the elastic modulus and hardness of the surface glass layer were higher than those of the dense Y-TZP layer. The mean SBS values for the graded glass-zirconia structure and veneering porcelain (24.35 ± 0.40 MPa) were statistically higher than those of zirconia and veneering porcelain (9.22 ± 0.20 MPa) (Pzirconia structure can be fabricated by the glass infiltration/densification technique, and this structure exhibits a strong core-veneer bond. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. The effect of hydrofluoric acid surface treatment and bond strength of a zirconia veneering ceramic.

    Science.gov (United States)

    Chaiyabutr, Yada; McGowan, Steve; Phillips, Keith M; Kois, John C; Giordano, Russell A

    2008-09-01

    Clinicians are frequently faced with a challenge in selecting materials for adjacent restorations, particularly when one tooth requires a zirconia-based restoration and the next requires a veneer. While it may be desirable to use the same veneering ceramic on adjacent teeth, little information is available about the use of veneering ceramics over a zirconia-based material. The purpose of this study was threefold: (1) to study the influence of hydrofluoric acid-etched treatment on the surface topography of the zirconia veneering ceramic, (2) to test the bond strength of zirconia veneering ceramic to enamel, and (3) to evaluate the flexural strength and the elemental composition of ceramic veneers. Three zirconia veneering ceramics (Cerabien CZR (CZ), Lava Ceram (L), and Zirox (Z)) and 4 conventional veneering ceramics (Creation (C), IPS d.Sign (D), Noritake EX-3 (E), and Reflex (R)) were evaluated. Twenty ceramic bars of each material were fabricated and surface treated with hydrofluoric acid according to the manufacturer's recommendations. Ten specimens from each group of materials were examined with a profilometer, and a sample of this group was selected for quantitative evaluation using a scanning electron microscope (SEM). Another 10 acid-etched specimens from each group of materials were treated with silane prior to cementing with resin cement (Variolink II) on enamel surfaces. These luted specimens were loaded to failure in a universal testing machine in the shear mode with a crosshead speed of 0.05 mm/min. The data were analyzed with a 1-way ANOVA, followed by Tukey's HSD test (alpha=.05). An additional 10 ceramic bars from each material group were fabricated to evaluate flexural strength and elemental composition. The flexural strength (MPa) of each specimen was determined by using a 4-point-1/4-point flexure test. A Weibull statistic tested the reliability of the strength data; pairwise differences among the 7 groups were evaluated at confidence intervals

  10. Interaction of oxygen with zirconia surface

    International Nuclear Information System (INIS)

    Ivankiv, L.I.; Ketsman, I.V.

    1999-01-01

    The influence of surface heat treatment, electron (50-800) eV irradiation and UV (180-300) nM illumination of adsorption system on the state of oxygen adsorbed on zirconia surface have been investigated. On the basis of experimental results obtained by investigation of photon emission accompanying oxygen adsorption (AL) and TPD data existence of adsorption sites on the surface is suggested on which irreversible dissociative adsorption of oxygen occurs. These very sites are associated with emission processes Conclusion is made that the only type of adsorption sites connected with anion vacancy is present on zirconia surface and this is its charge state that determines the state of adsorbed oxygen. One of the important mechanisms by which the electron and UV photon excitation affects the adsorption interaction is the change of the charge state of the adsorption site

  11. Chemical treatment and biomimetic coating evaluating in zirconia-alumina ceramics; Avaliacao de tratamentos quimicos e recobrimento biomimetico em ceramicas de alumina-zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Amanda Abati

    2007-07-01

    Ceramic materials, as alumina and zirconia have been explored along the years as biomaterials application. The bio inert nature has been stimulating the development of new alternatives, as chemical treatments to improve the biological application of these ceramics. The biomimetic process of bio inert ceramics for coating apatite is based on soaking the implant in a simulated body fluid, SBF, with ion concentrations nearly equal to those of human blood plasma. The bioactivity of the material is related with the formation of a layer constituted of hydroxyapatite low crystalline, similar to the biological apatite. The biocompatibility associated to the structural properties of the alumina and zirconia has been stimulating the clinical use of these materials, mainly in areas of larger mechanical requests, places not recommended for bioactive hydroxyapatite, for instance. In this work samples of alumina, zirconia doped with Yttria (3% mol) and composites of alumina and zirconia doped with Yttria (3% mol) were prepared by co-precipitation method, calcinate, sintered, chemically treated with solutions of acid phosphoric and sodium hydroxide and them immersed in 1.0 M and 1.5 M SBF. The calcinate powders were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), gas adsorption (BET) and laser diffraction. The XRD results indicate that the samples are low crystalline. It was observed for BET that the samples present high specific surface area. The results of laser diffraction and SEM showed that the powders are agglomerates. The sintered samples were analyzed by XRD, SEM and X-ray fluorescence (XRF). The phases quantified by Rietveld method were: cubic, tetragonal and monoclinic of the zirconia, besides the phase alpha of the alumina. The chemical treatment with phosphoric acid didn't present a tendency of larger apatite formation in relation to the samples no chemically treated. The treatment with sodium hydroxide provoked accentuated transformation

  12. Use of Biomass as a Sustainable and Green Fuel with Alkali-Resistant DeNOx Catalysts based on Sulfated or Tungstated Zirconia

    DEFF Research Database (Denmark)

    Due-Hansen, Johannes; Fehrmann, Rasmus; Christensen, Claus H.

    Use of biomass as an alternative to fossil fuels has achieved increasing interest since it does not contribute to CO2 accumulation in the atmosphere. Over the past 10-15 years, heat and electricity production from biomass has increased to almost 7% of all energy supply in the European Union...... and is expected to increase further. The by far most efficient use of solid bio-resources in energy production is combustion in combined biomass and coal or oil-fired power plants. However, in such applications nitrogen oxides are inevitably present in the flue gases. Selective catalytic reduction (SCR...... of alternative catalysts that are more resistant towards poisoning with potassium. Since deactivation with alkali additives generally occurs due to strong acid-base interaction with the V-OH sites responsible for the activated ammonia adsorption, one possible way to increase catalyst resistance to alkaline...

  13. Retention Forces between Titanium and Zirconia Components of Two-Part Implant Abutments with Different Techniques of Surface Modification.

    Science.gov (United States)

    von Maltzahn, Nadine Freifrau; Holstermann, Jan; Kohorst, Philipp

    2016-08-01

    The adhesive connection between titanium base and zirconia coping of two-part abutments may be responsible for the failure rate. A high mechanical stability between both components is essential for the long-term success. The aim of the present in-vitro study was to evaluate the influence of different surface modification techniques and resin-based luting agents on the retention forces between titanium and zirconia components in two-part implant abutments. A total of 120 abutments with a titanium base bonded to a zirconia coping were investigated. Two different resin-based luting agents (Panavia F 2.0 and RelyX Unicem) and six different surface modifications were used to fix these components, resulting in 12 test groups (n = 10). The surface of the test specimens was mechanically pretreated with aluminium oxide blasting in combination with application of two surface activating primers (Alloy Primer, Clearfil Ceramic Primer) or a tribological conditioning (Rocatec), respectively. All specimens underwent 10,000 thermal cycles between 5°C and 55°C in a moist environment. A pull-off test was then conducted to determine retention forces between the titanium and zirconia components, and statistical analysis was performed (two-way anova). Finally, fracture surfaces were analyzed by light and scanning electron microscopy. No significant differences were found between Panavia F 2.0 and RelyX Unicem. However, the retention forces were significantly influenced by the surface modification technique used (p zirconia copings were pretreated with aluminium oxide blasting, and with the application of Clearfil Ceramic Primer. Surface modification techniques crucially influence the retention forces between titanium and zirconia components in two-part implant abutments. All adhesion surfaces should be pretreated by sandblasting. Moreover, a phosphate-based primer serves to enhance long-term retention of the components. © 2015 Wiley Periodicals, Inc.

  14. Making yttria-stabilized tetragonal zirconia translucent

    Science.gov (United States)

    Zhang, Yu

    2014-01-01

    Objective The aim of this study was to provide a design guideline for developing tetragonal yttria-stabilized zirconia with improved translucency. Methods The translucency, the in-line transmission in particular, of 3 mol.% yttria-stabilized tetragonal zirconia (3Y-TZP) has been examined using the Rayleigh scattering model. The theory predicts that the in-line transmission of 3Y-TZP can be related to its thickness with grain size and birefringence the governing parameters. To achieve a threshold value of translucency, the critical grain size of 3Y-TZP was predicted for various thicknesses (0.3 – 2.0 mm). The threshold value was defined by a measured average in-line transmission value of a suite of dental porcelains with a common thickness of 1 mm. Our theoretical predictions were calibrated with one of the very few experimental data available in the literature. Results For a dense, high-purity zirconia, its in-line transmission increased with decreasing grain size and thickness. To achieve a translucency similar to that of dental porcelains, a nanocyrstalline 3Y-TZP structure was necessitated, due primarily to its large birefringence and high refractive index. Such a grain size dependence became more pronounced as the 3Y-TZP thickness increased. For example, at a thickness of 1.3 mm, the mean grain size of a translucent 3Y-TZP should be 82 nm. At 1.5 mm and 2 mm thicknesses, the mean grain size needed to be 77 nm and 70 nm, respectively. Significance A promising future for zirconia restorations, with combined translucency and mechanical properties, can be realized by reducing its grain size. PMID:25193781

  15. Pilot evaluation of resin composite cement adhesion to zirconia using a novel silane system.

    Science.gov (United States)

    Matinlinna, Jukka P; Lassila, Lippo V J; Vallittu, Pekka K

    2007-02-01

    In this study, we evaluated the effect of two silane coupling agents and their blends with a cross-linker silane on the bond strength of a dimethacrylate-based resin composite cement to surface-conditioned zirconia. A total of 40 planar zirconia specimens were used for 8 test groups. After alumina particle abrasion, followed by tribochemical silica-coating, the specimens were randomly assigned to four silanizations: with 1.0 vol% 3-methacryloyloxypropyltrimethoxysilane or 1.0 vol% 3-mercaptopropyltrimethoxysilane or their blends with 1.0 vol% 1,2-bis-(triethoxysilyl)ethane (all in ethanol/water). The resin composite (RelyX ARC, 3M ESPE) stubs (n=10/group) were light-polymerized onto zirconia specimens. Four test groups were tested without water storage and 4 thermo-cycled at 6000 cycles (5+/-1 degrees C to 55+/-1 degrees C), with a dwelling time of 30 s. The shear bond strength of the cement stubs to zirconia was measured using a universal testing machine at a constant cross-head speed of 1 mm/min. Scanning electron microscopy was employed for imaging the zirconia surface after conditioning and testing. Failure mode was evaluated visually. A surface chemical analysis was carried out with the EDXA system. The highest shear bond strength was 21.9+/-8.7 MPa, obtained with a blend of 3-mercaptopropyltrimethoxysilane and 1,2-bis-(triethoxysilyl)ethane (dry storage), and 16.0+/-1.5 MPa, with 3-methacryloyloxypropyltrimethoxysilane (thermo-cycled). Thermo-cycling decreased the bond strengths significantly (ANOVA, pethane.

  16. Effects of Mechanical and Chemical Pretreatments of Zirconia or Fiber Posts on Resin Cement Bonding

    Science.gov (United States)

    Li, Rui; Zhou, Hui; Wei, Wei; Wang, Chen; Sun, Ying Chun; Gao, Ping

    2015-01-01

    The bonding strength between resin cement and posts is important for post and core restorations. An important method of improving the bonding strength is the use of various surface pretreatments of the post. In this study, the surfaces of zirconia (fiber) posts were treated by mechanical and/or chemical methods such as sandblasting and silanization. The bonding strength between the zirconia (fiber) post and the resin cement was measured by a push-out method after thermocycling based on the adhesion to Panavia F 2.0 resin cement. The zirconia and fiber posts exhibited different bonding strengths after sandblasting and/or silanization because of the different strengths and chemical structures. The zirconia post showed a high bonding strength of up to 17.1 MPa after a combined treatment of sandblasting and silanization because of the rough surface and covalent bonds at the interface. This effect was also enhanced by using 1,2-bis(trimethoxysilyl)ethane for the formation of a flexible layer at the interface. In contrast, a high bonding strength of 13.9 MPa was obtained for the fiber post treated by silane agents because the sandblasting treatment resulted in damage to the fiber post, as observed by scanning electron microscopy. The results indicated that the improvement in the bonding strength between the post and the resin cement could be controlled by different chemical and/or mechanical treatments. Enhanced bonding strength depended on covalent bonding and the surface roughness. A zirconia post with high bonding strength could potentially be used for the restoration of teeth in the future. PMID:26066349

  17. Curing efficiency of dual-cure resin cement under zirconia with two different light curing units.

    Science.gov (United States)

    Gultekin, Pınar; Pak Tunc, Elif; Ongul, Deger; Turp, Volkan; Bultan, Ozgur; Karataslı, Burcin

    2015-01-01

    Adequate polymerization is a crucial factor in obtaining optimal physical properties and a satisfying clinical performance from composite resin materials. The aim of this study was to evaluate the polymerization efficiency of dual-cure resin cement cured with two different light curing units under zirconia structures having differing thicknesses. 4 zirconia discs framework in 4 mm diameter and in 0.5 mm, 1 mm and 1.5 mm thickness were prepared using computer-aided design system. One of the 0.5 mm-thick substructures was left as mono-layered whereas others were layered with feldspathic porcelain of same thickness and ceramic samples with 4 different thicknesses (0.5, 1, 1.5 and 2.0 mm) were prepared. For each group (n=12) resin cement was light cured in polytetrafluoroethylene molds using Light Emitting Diode (LED) or Quartz-Tungsten Halogen (QHT) light curing units under each of 4 zirconia based discs (n=96). The values of depth of cure (in mm) and the Vickers Hardness Number values (VHN) were evaluated for each specimen. The use of LED curing unit produced a greater depth of cure compared to QTH under ceramic discs with 0.5 and 1 mm thickness (punit produced significantly greater VHN values compared to the QTH unit (pLight curing may not result in adequate resin cement polymerization under thick zirconia structures. LED light sources should be preferred over QTH for curing dual-cure resin cements, especially for those under thicker zirconia restorations.

  18. CURING EFFICIENCY OF DUAL-CURE RESIN CEMENT UNDER ZIRCONIA WITH TWO DIFFERENT LIGHT CURING UNITS

    Directory of Open Access Journals (Sweden)

    Pınar GÜLTEKİN

    2015-04-01

    Full Text Available Purpose: Adequate polymerization is a crucial factor in obtaining optimal physical properties and a satisfying clinical performance from composite resin materials. The aim of this study was to evaluate the polymerization efficiency of dual-cure resin cement cured with two different light curing units under zirconia structures having differing thicknesses. Materials and Methods: 4 zirconia discs framework in 4 mm diameter and in 0.5 mm, 1 mm and 1.5 mm thickness were prepared using computer-aided design system. One of the 0.5 mm-thick substructures was left as mono-layered whereas others were layered with feldspathic porcelain of same thickness and ceramic samples with 4 different thicknesses (0.5, 1, 1.5 and 2.0 mm were prepared. For each group (n=12 resin cement was light cured in polytetrafluoroethylene molds using Light Emitting Diode (LED or Quartz-Tungsten Halogen (QHT light curing units under each of 4 zirconia based discs (n=96. The values of depth of cure (in mm and the Vickers Hardness Number values (VHN were evaluated for each specimen. Results: The use of LED curing unit produced a greater depth of cure compared to QTH under ceramic discs with 0.5 and 1 mm thickness (p<0.05.At 100μm and 300 μm depth, the LED unit produced significantly greater VHN values compared to the QTH unit (p<0.05. At 500 μm depth, the difference between the VHN values of LED and QTH groups were not statistically significant. Conclusion: Light curing may not result in adequate resin cement polymerization under thick zirconia structures. LED light sources should be preferred over QTH for curing dual-cure resin cements, especially for those under thicker zirconia restorations.

  19. Effect of Three Different Core Materials on Masking Ability of a Zirconia Ceramic

    Directory of Open Access Journals (Sweden)

    Farhad Tabatabaian

    2016-12-01

    Full Text Available Objectives: Masking ability of a restorative material plays a role in hiding colored substructures; however, the masking ability of zirconia ceramic (ZRC has not yet been clearly understood in zirconia-based restorations. This study evaluated the effect of three different core materials on masking ability of a ZRC.Materials and Methods: Ten zirconia disc samples, 0.5mm in thickness and 10mm in diameter, were fabricated. A white (W substrate (control and three substrates of nickel-chromium alloy (NCA, non-precious gold alloy (NPGA, and ZRC were prepared. The zirconia discs were placed on the four types of substrates for spectrophotometry. The L*, a*, and b* values of the specimens were measured by a spectrophotometer and color change (ΔE values were calculated to determine color differences between the test and control groups and were then compared with the perceptual threshold. Randomized block ANOVA and Bonferroni test analyzed the data. A significance level of 0.05 was considered.Results: The mean and standard deviation values of ΔE for NCA, NPGA, and ZRC groups were 10.26±2.43, 9.45±1.74, and 6.70±1.91 units, respectively. Significant differences were found in the ΔE values between ZRC and the other two experimental groups (NCA and NPGA; P<0.0001 and P=0.001, respectively. The ΔE values for the groups were more than the predetermined perceptual threshold.Conclusions: Within the limitations of this study, it was concluded that the tested ZRC could not well mask the examined core materials.Keywords: Color; Spectrophotometry; Visual Perception; Yttria Stabilized Tetragonal Zirconia

  20. Effect of LASER Irradiation on the Shear Bond Strength of Zirconia Ceramic Surface to Dentin

    Directory of Open Access Journals (Sweden)

    Sima Shahabi

    2012-09-01

    Full Text Available Background and Aims: Reliable bonding between tooth substrate and zirconia-based ceramic restorations is always of great importance. The laser might be useful for treatment of ceramic surfaces. The aim of the present study was to investigate the effect of laser irradiation on the shear bond strength of zirconia ceramic surface to dentin. Materials and Methods: In this experimental in vitro study, 40 Cercon zirconia ceramic blocks were fabricated. The surface treatment was performed using sandblasting with 50-micrometer Al2O3, CO2 laser, or Nd:YAG laser in each test groups. After that, the specimens were cemented to human dentin with resin cement. The shear bond strength of ceramics to dentin was determined and failure mode of each specimen was analyzed by stereo-microscope and SEM investigations. The data were statistically analyzed by one-way analysis of variance and Tukey multiple comparisons. The surface morphology of one specimen from each group was investigated under SEM. Results: The mean shear bond strength of zirconia ceramic to dentin was 7.79±3.03, 9.85±4.69, 14.92±4.48 MPa for CO2 irradiated, Nd:YAG irradiated, and sandblasted specimens, respectively. Significant differences were noted between CO2 (P=0.001 and Nd:YAG laser (P=0.017 irradiated specimens with sandblasted specimens. No significant differences were observed between two laser methods (P=0.47. The mode of bond failure was predominantly adhesive in test groups (CO2 irradiated specimens: 75%, Nd:YAG irradiated: 66.7%, and sandblasting: 41.7%. Conclusion: Under the limitations of the present study, surface treatment of zirconia ceramics using CO2 and Nd:YAG lasers was not able to produce adequate bond strength with dentin surfaces in comparison to sandblasting technique. Therefore, the use of lasers with the mentioned parameters may not be recommended for the surface treatment of Cercon ceramics.

  1. Effect of zirconia surface treatment on zirconia/veneer interfacial toughness evaluated by fracture mechanics method.

    Science.gov (United States)

    Wang, Gaoqi; Zhang, Song; Bian, Cuirong; Kong, Hui

    2014-07-01

    The aim of this study was to evaluate the effect of the airborne-particle abrasion and liner application on the interfacial toughness between veneering porcelain and zirconia core by means of a fracture mechanics test. Beam-shaped zirconia specimens were sectioned and divided into 4 groups according to different surface treatments as follows: Group C (control): no treatment; Group L: application of liner; Group A: airborne-particle abrasion with Al2O3 (sandblasting); and Group AL: airborne-particle abrasion and application of liner. The zirconia surfaces before and after sandblasting were observed and analyzed by SEM and white light interferometer. Specimens of each pretreated group were veneered with 3 core/veneer thickness ratios of 2:3, 1:1, and 3:2, corresponding to 3 phase angles respectively. Fracture mechanics test was performed on each specimen, the energy release rate G and phase angle ψ were calculated to characterize interfacial toughness. The experimental data were analyzed statistically using three-way ANOVA and the Tukey's HSD test. The surfaces of fractured specimens were examined by SEM and EDX. At each phase angle, the interfaces with no treatment had higher mean G values than that of other groups. All the specimens showed mixed failure mode with residual veneer or liner on the zirconia surfaces. The toughness of zirconia/veneer interface with no treatment is significantly higher than that of interfaces subjected to liner application and airborne-particle abrasion. Liner application and airborne-particle abrasion seem to reduce zirconia/veneer interfacial toughness. Therefore, the two surface treatment methods should be applied with caution. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. High energy milling of zirconia-titania powders synthesized by coprecipitation; Moagem de alta energia em pos de zirconia-titania sintetizados por co-precipitacao

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Cristiano M.B.; Marchi, Juliana; Lazar, Dolores R.R.; Ussui, Valter, E-mail: vussui@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    Zirconia based ceramics are known by its remarkable mechanical properties as hardness and fracture toughness and in biomedical applications are classified as bioinert. By its turn, titania ceramics has been studied due to its ability to bond directly to bone tissue, but are structurally brittle. Properties of ceramics are strongly dependent of physical and chemical characteristics of its former powders. In the present work, research done for the synthesis of zirconia-titania ceramics by the coprecipitation route are presented, emphasizing the conditioning process through a high energy milling in a atritor mill, classifying of powders in vibratory sieves and forming of cylindrical ceramic samples followed by a sintering process at 1500 deg C for 01 hour. The intermediary samples produced in the various steps of the process were characterized by scanning electronic microscope, X-ray diffraction, nitrogen gas adsorption and granulometric analysis. (author)

  3. Aging resistance of surface-treated dental zirconia.

    Science.gov (United States)

    Inokoshi, Masanao; Vanmeensel, Kim; Zhang, Fei; De Munck, Jan; Eliades, George; Minakuchi, Shunsuke; Naert, Ignace; Van Meerbeek, Bart; Vleugels, Jozef

    2015-02-01

    The influence of surface treatment on the low-temperature degradation (LTD) of tetragonal zirconia polycrystalline (TZP) is still unclear. The effect of surface treatments on the LTD behavior of zirconia was investigated. Fully-sintered specimens of seven commercial dental zirconia (Aadva, GC; In-CeramYZ, VITA; IPS e.max ZirCAD, Ivoclar Vivadent; LAVA Frame and LAVA Plus, 3M ESPE; NANOZR, Panasonic; ZirTough, Kuraray Noritake) were provided by the manufacturers with specimen dimensions of approximately 10mm×5mm×3mm. For each zirconia grade, samples were kept 'as sintered' (untreated) or were subjected to one of the three surface treatments: rough polished, sandblasted with Al2O3, tribochemical silica sandblasted (n=3/group). The tetragonal to monoclinic transformation was evaluated by X-ray diffraction at several intervals during LTD testing up to 40h in steam in an autoclave (134°C, 2bar). The five yttria-stabilized TZP (Y-TZP: Aadva, In-CeramYZ, IPS e.max ZirCAD, LAVA Frame, LAVA Plus) zirconia showed a similar trend in LTD behavior. The Al2O3 sandblasted zirconia showed the highest monoclinic volume fraction. The as sintered (untreated) zirconia degraded faster than the surface-treated zirconia. Although the surface-treated ceria-stabilized TZP/alumina (Ce-TZP/Al2O3: NANOZR) zirconia had a higher initial monoclinic volume fraction compared to the Y-TZP zirconia, it showed a stronger aging resistance. The as sintered (untreated) Y-TZP/alumina (Y-TZP/Al2O3: ZirTough) zirconia showed a strong aging resistance, whereas the surface-treated Y-TZP/Al2O3 zirconia degraded slightly. Surface treatment improved the aging resistance of Y-TZP zirconia. Surface treatment did not affect the LTD behavior of Ce-TZP/Al2O3 zirconia, while surface treatment decreased the aging resistance of Y-TZP/Al2O3 zirconia. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. Electrical characterization of zirconia-niobium and zirconia-titanium composites

    International Nuclear Information System (INIS)

    Reis, S.T. dos.

    1993-01-01

    Zirconia-niobium and zirconia-titanium composites were made by powder mixing, cold pressing, and vacuum sintering at 1600 0 C. The metallic particles were added in the proportion of 0-50% by volume. Electrical resistivity measurements were performed by the two probes and the four probes d.c. method as a function of metallic particle concentration. Electrical resistivity of these composites decreased sharply in the region of 30-40 vol% Nb or Ti, in agreement with the percolation theory. Tests in an induction furnace were performed to check the self-heating response of these composites. (author). 33 refs, 40 figs, 11 tabs

  5. Multifunctional switches based on bis-imidazole derivative

    Indian Academy of Sciences (India)

    Administrator

    the coloured species make the derivative a candidate for applications in optical data storage. Acknowledgements. The authors wish to thank King Abdul Aziz City for. Science and Technology (KACST) for funding this research work via grant no. At–27-68. References. 1. Gust D, Moore T A and Moore A L 2001 Acc. Chem.

  6. Coordination of Tridentate Schiff Base Derivatives of 4 ...

    African Journals Online (AJOL)

    NICO

    KEYWORDS. Tridentate, rhenium(V), imido, crystal structures. 1. Introduction. The research interest in pyrazolone (pz) and its derivatives is mainly due to their pharmaceutical properties. Pz is a five-membered lactam ring, containing two nitrogen atoms and a ketone, and it is an active moiety in pharmacology, such as for.

  7. The development of zirconia membrane oxygen separation technology

    International Nuclear Information System (INIS)

    Chiacchi, F.T.; Badwal, S.P.S.; Velizko, V.

    2000-01-01

    The oxygen separation technology based on ceramic membranes constructed from stabilised zirconia is currently under development for applications ranging from oxygen generation or air enrichment for medical use to control of oxygen concentration or oxygen removal from gas streams and enclosures for semiconductor, food packaging and process control instrumentation industries. The technology is based on a rugged tubular design with extensive thermal cycling capability. Several single and three tube devices have been operated for periods up to 5000h. An eight tube module, as a building block for larger scale oxygen production or removal devices, has been constructed and is being evaluated. In this paper, the construction of the device, oxygen generating capacity, life time tests and performance of the ceramic membrane device under development at CSIRO will be discussed. Copyright (2000) The Australian Ceramic Society

  8. Isomerization-cracking of n-octane on catalysts based on heteropolyacid H3Pw12O40 and heteropolyacid supported on zirconia and promoted with Pt and Cs

    International Nuclear Information System (INIS)

    Manuele, Debora L.; Torres, Gerardo C.; Benitez, Viviana M.; Badano, Juan M.; Yori, Juan C.; Sepulveda, Jorge H.

    2013-01-01

    Isomerization-cracking of n-octane was studied using H 3 PW 12 O 40 (HPA) and HPA supported on zirconia and promoted with Pt and Cs. The addition of Pt and Cs to the supported HPA did not modify the Keggin structure. The Pt addition to the supported HPA did not substantially modify the total acidity; however, the Broensted acidity increased significantly. Cs increased the total acidity and Broensted acidity. A linear relation was observed between the n-C 8 total conversion and Broensted acidity. The most adequate catalysts for performing isomerization and cracking to yield high research octane number (RON) are those with higher values of Broensted acidity. (author)

  9. High-strength CAD/CAM-fabricated veneering material sintered to zirconia copings--a new fabrication mode for all-ceramic restorations.

    Science.gov (United States)

    Beuer, Florian; Schweiger, Josef; Eichberger, Marlis; Kappert, Heinrich F; Gernet, Wolfgang; Edelhoff, Daniel

    2009-01-01

    With this in vitro study the fracture strength of zirconia-based crown copings being veneered with a CAD/CAM generated high-strength ceramic cap by sintering is compared with anatomically identical zirconia-based crowns, which were either overpressed or veneered by the layering technique for completion. A 1.2mm, 360 degrees chamfer preparation was performed on a second maxillary molar and was dublicated 15 times in a cobalt-chromium-alloy. A sample of 45 zirconia copings was produced and divided into three groups. In the first group (VT) zirconia copings received conventional veneering in layering technique, in the second group the veneering porcelain was pressed over the zirconia coping (PT), and for the third group (ST) a CAD/CAM-fabricated high-strength anatomically shaped veneering cap was sintered onto the zirconia coping. All crowns were cemented conventionally onto their dies and tested in the universal testing machine until clinical failure. The fracture load data were compared by a one-way analysis of variance and a multiple comparison posthoc test (alphacrowns and fixed partial dentures with a potential lower risk of chippings.

  10. [Semisynthetic cellulose derivatives as the base of hydrophilic gel systems].

    Science.gov (United States)

    Bajerová, M; Gajdziok, J; Dvorácková, K; Masteiková, R; Kollár, P

    2008-04-01

    The field of drug technology widely ulilizes gel systems of high-molecular substances, which have a number of advantages, such as low toxicity, availability, unique physical properties, biocompatibility, mucoadhesivity, and others. Gel systems are used in the field of local as well as general therapy, in both shape-specific and shape-non-specific dosage forms, in medicaments of the first, second, and third generations. An important group of gels employed in pharmacy are hydrophilic gels or hydrogels, most frequently composed of hydrophilic polymers of natural, semisynthetic and synthetic origin. Though cellulose derivatives as the representatives of polymers of semisynthetic origin are used in pharmaceutical technology for a long time, their research continues and their other possible uses are being searched for. Their advantages include especially safety, easy availability, and a relatively low price. The review paper describes selected cellulose derivatives, their properties and uses in pharmaceutical technology with regard to their use in the field of production of gel systems.

  11. Synthesis and characterization of mullite–zirconia composites by ...

    Indian Academy of Sciences (India)

    Mullite–zirconia composites containing 10–30 wt% zirconia were prepared by reaction sintering of zircon flour, sillimanite beach sand and calcined alumina. Raw materials were attrition milled, shaped into pellets and bars and sintered in the temperature range of 1450–1600°C with 2 h soaking at peak temperature.

  12. Dynamic simulation of carbochlorination of zirconia in a pilot plant ...

    African Journals Online (AJOL)

    Zirconium tetrachloride was produced via the chlorination of zirconia in a fluidized bed reactor in the presence of carbon. The fluidized bed zirconia carbochlorination reactor was modeled dynamically via a three-phase hydrodynamic flow assumption. The operating temperature (800-1200 °C), reaction time (30-120 min) ...

  13. Characterization of combustion synthesized zirconia powder by UV ...

    Indian Academy of Sciences (India)

    Unknown

    The modified versions of zirconium dioxide, viz. the sulfated ZrO2, zirconia substituted mixed oxides such as CexZr1–xO2 solid solutions (0 ≤ x ≤ 1), various transition metal stabilized zirconia and hydrous zirconium oxide have been reported to be effective for several organic reactions, combustion and gas phase reactions.

  14. Osseointegration of a Zirconia Implant : A Histologic Assessment

    NARCIS (Netherlands)

    Schepke, Ulf; Meijer, Gert J; Meijer, Henny Ja; Walboomers, X Frank; Cune, Marco

    2017-01-01

    PURPOSE: The aim of this study was to describe the histologic and histomorphometric features of a retrieved, functional endosseous zirconia implant in a human subject. MATERIALS AND METHODS: A maxillary zirconia implant (ZV3) placed in a 52-year-old man was retrieved after 2 years of uncompromised

  15. Retentive strength of two-piece CAD/CAM zirconia implant abutments.

    Science.gov (United States)

    Gehrke, Peter; Alius, Jochen; Fischer, Carsten; Erdelt, Kurt J; Beuer, Florian

    2014-12-01

    The purpose of this study is to evaluate the retention of two-piece computer-aided design (CAD)/computer aided manufacturing (CAM) zirconia abutments after artificial aging under simulated oral conditions using three different types of resin-based luting agents. Twenty-one CAD/CAM-generated zirconia copings (CERCON Compartis, Degudent, Hanau, Germany) were bonded to a prefabricated secondary titanium implant insert (XiVE Ti-Base, Dentsply Friadent, Mannheim, Germany), using three different types of resin-based luting agents: group A: Panavia 21 (Kuraray Co, Kurashiki, Japan); group B: Multilink Implant (Ivoclar Vivadent, Schaan, Liechtenstein); and group C: SmartCem2 (Dentsply DeTrey, Konstanz, Germany). The bonding surfaces of the titanium inserts and the zirconia ceramic copings were air-abraded and cleaned in alcohol. All specimens were stored in distilled water for 60 days and subsequently thermal-cycled 15,000 times (5-55 °C). The dislodging force of the copings along the long axis of the implant/abutment complex was recorded using a universal testing machine with 2 mm/min crosshead speed. Data were analyzed descriptively and by performing the Kruskal-Wallis test. The mean retention values were 924.93 ± 363.31 N for Panavia 21, 878.05 ± 208.33 N for Multilink Implant, and 650.77 ± 174.92 N for SmartCem2. The Kruskal-Wallis test indicated no significant difference between the retention values of the tested luting agents (p = 0.1314). The failure modes of all tested two-piece abutments were completely adhesive, leaving the detached zirconia coping and titanium insert undamaged. The use of resin-based luting agents in combination with air abrasion of titanium inserts and zirconia copings led to a stable retention of two-piece CAD/CAM abutments. The bonding stability of the investigated luting agents exceeded the general limits of fracture resistance of two-piece zirconia abutments. A notable difference between the mean retention values of the tested bond

  16. Internal Nano Voids in Yttria-Stabilised Zirconia (YSZ Powder

    Directory of Open Access Journals (Sweden)

    Chen Barad

    2017-12-01

    Full Text Available Porous yttria-stabilised zirconia ceramics have been gaining popularity throughout the years in various fields, such as energy, environment, medicine, etc. Although yttria-stabilised zirconia is a well-studied material, voided yttria-stabilised zirconia powder particles have not been demonstrated yet, and might play an important role in future technology developments. A sol-gel synthesis accompanied by a freeze-drying process is currently being proposed as a method of obtaining sponge-like nano morphology of embedded faceted voids inside yttria-stabilised zirconia particles. The results rely on a freeze-drying stage as an effective and simple method for generating nano-voided yttria-stabilised zirconia particles without the use of template-assisted additives.

  17. Zirconia as a sliding material: histologic, laboratory, and clinical data.

    Science.gov (United States)

    Cales, B

    2000-10-01

    Zirconia ceramics have been introduced in orthopaedic surgery as prosthetic femoral heads to solve the critical issue of femoral head fractures sometimes observed with alumina ceramics. In addition to outstanding mechanical properties, zirconia ceramics have, similar to other surgical grade ceramics, a high biocompatibility and a high resistance to scratching. The radioactivity of zirconia ceramic, which has been the subject of contradictory data, now is well understood and managed with appropriate standards. The long-term stability of zirconia ceramics recently has been studied extensively and precise models allow a good prediction of their long-term behavior. In vitro wear tests against polyethylene and clinical data confirm the low wear rate associated with the use of ceramic femoral heads. The use of zirconia femoral heads in ceramic-on-ceramic total hip prostheses also has been investigated and now is clinically effective.

  18. Effect of Resin Cement Mixing Method on the Retention Strength of a CAD/CAM Zirconia Crowns

    OpenAIRE

    Sadighpour, Leyla; Fazel, Akbar; Geramipanah, Farideh; Allahdadi, Mahdi

    2014-01-01

    Several treatments have been suggested to improve the retention of zirconia-based restorations luted with different cements. Resin cements are believed to improve crown retention under certain circumstances. The aim of the present study was to examine the effect of three cements with different mixing methods on the retention of CAD/CAM zirconia crowns. Thirty extracted human molars were randomly divided into three groups and prepared for all-ceramic crowns (6° taper, 4-mm height and a 1.2 mm ...

  19. Effects of yttrium, aluminum and chromium concentrations in bond coatings on the performance of zirconia-yttria thermal barriers

    Science.gov (United States)

    Stecura, S.

    1980-01-01

    A cyclic furnace study was conducted on thermal barrier systems to evaluate the effects of yttrium, chromium and aluminum in nickel-base alloy bond coatings and the effect of bond coating thickness on yttria-stabilized zirconia thermal barrier coating life. Without yttrium in the bond coatings, the zirconia coatings failed very rapidly. Increasing chromium and aluminum in the Ni-Cr-Al-Y bond coatings increased total coating life. This effect was not as great as that due to yttrium. Increased bond coat thickness was also found to increase life.

  20. Wear properties of alumina/zirconia composite ceramics for joint prostheses measured with an end-face apparatus.

    Science.gov (United States)

    Morita, Yusuke; Nakata, Kenichi; Kim, Yoon-Ho; Sekino, Tohru; Niihara, Koichi; Ikeuchi, Ken

    2004-01-01

    While only alumina is applied to all-ceramic joint prostheses at present, a stronger ceramic is required to prevent fracture and chipping due to impingement and stress concentration. Zirconia could be a potential substitute for alumina because it has high strength and fracture toughness. However, the wear of zirconia/zirconia combination is too high for clinical use. Although some investigations on composite ceramics revealed that mixing of different ceramics was able to improve the mechanical properties of ceramics, there are few reports about wear properties of composite ceramics for joint prosthesis. Since acetabular cup and femoral head of artificial hip joint are finished precisely, they indicate high geometric conformity. Therefore, wear test under flat contact was carried out with an end-face wear testing apparatus for four kinds of ceramics: alumina monolith, zirconia monolith, alumina-based composite ceramic, and zirconia based composite ceramic. Mean contact pressure was 10 MPa and sliding velocity was 40 mm/s. The wear test continued for 72 hours and total sliding distance was 10 km. After the test, the wear factor was calculated. Worn surfaces were observed with a scanning electron micrograph (SEM). The results of this wear test show that the wear factors of the both composite ceramics are similarly low and their mechanical properties are much better than those of the alumina monolith and the zirconia monolith. According to these results, it is predicted that joint prostheses of the composite ceramics are safer against break down and have longer lifetime compared with alumina/alumina joint prostheses.

  1. Fracture Strength After Fatigue Loading of Lithium Disilicate Pressed Zirconia Crowns.

    Science.gov (United States)

    Kim, So-Yeun; Choi, Jae-Won; Ju, Sung-Won; Ahn, Jin-Soo; Yoon, Mi-Jung; Huh, Jung-Bo

    2016-01-01

    The aim of this study was to evaluate the fracture resistance of fatigued lithium disilicate pressed zirconia crowns versus other ceramic crowns. Lithium disilicate pressed zirconia, fluorapatite pressed zirconia, monolithic lithium disilicate, and monolithic zirconia crowns were fabricated. Cyclic and static loadings were applied to the mesiobuccal cusp tip after thermocycling and fracture strengths were recorded. Fatigued lithium disilicate pressed zirconia crowns were found to have a fracture resistance of 9,117.81 ± 727.04 N, compared with 9,240.61 ± 887.21 N for monolithic zirconia crowns, 3,030.18 ± 1,505.83 N for fluorapatite pressed zirconia crowns, and 4,173.94 ± 877.46 N for monolithic lithium disilicate crowns (P = .001). This in vitro study shows that fatigued lithium disilicate pressed zirconia and monolithic zirconia crowns have better fracture resistance than fluorapatite pressed zirconia and monolithic lithium disilicate crowns.

  2. Clinical assessment of enamel wear caused by monolithic zirconia crowns.

    Science.gov (United States)

    Stober, T; Bermejo, J L; Schwindling, F S; Schmitter, M

    2016-08-01

    The purpose of this study was to measure enamel wear caused by antagonistic monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia full molar crowns were placed in 20 patients. Patients with high activity of the masseter muscle at night (bruxism) were excluded. For analysis of wear, vinylpolysiloxane impressions were prepared after crown incorporation and at 6-, 12-, and 24-month follow-up. Wear of the occlusal contact areas of the crowns, of their natural antagonists, and of two contralateral natural antagonists (control teeth) was measured by use of plaster replicas and a 3D laser-scanning device. Differences of wear between the zirconia crown antagonists and the control teeth were investigated by means of two-sided paired Student's t-tests and linear regression analysis. After 2 years, mean vertical loss was 46 μm for enamel opposed to zirconia, 19-26 μm for contralateral control teeth and 14 μm for zirconia crowns. Maximum vertical loss was 151 μm for enamel opposed to zirconia, 75-115 μm for control teeth and 60 μm for zirconia crowns. Statistical analysis revealed significant differences between wear of enamel by zirconia-opposed teeth and by control teeth. Gender, which significantly affected wear, was identified as a possible confounder. Monolithic zirconia crowns generated more wear of opposed enamel than did natural teeth. Because of the greater wear caused by other dental ceramics, the use of monolithic zirconia crowns may be justified. © 2016 John Wiley & Sons Ltd.

  3. Effect of hydrothermal treatment on light transmission of translucent zirconias.

    Science.gov (United States)

    Putra, Armand; Chung, Kwok-Hung; Flinn, Brian D; Kuykendall, Tuesday; Zheng, Cheng; Harada, Kosuke; Raigrodski, Ariel J

    2017-09-01

    Studies of the light transmission of translucent zirconias after hydrothermal treatment are limited. The purpose of this in vitro study was to evaluate the effect of hydrothermal treatment on the light transmission of translucent zirconias for monolithic restorations. Four commercially available zirconia products, BruxZir Anterior Solid Zirconia (BruxAnt, BA), Lava Plus High Translucency (LPHT), Katana Zirconia Super Translucent (KST), and Katana Zirconia Ultra Translucent (KUT) were assessed and 1 type of lithium disilicate, e.max Press LT (LDLT) was used as a control. Plate specimens, 20×20×1 mm (n=80) for the translucency assessment were sectioned from postsintered zirconia bulk materials and ground with a #400-grit diamond wheel and coolant. The specimens were placed under hydrothermal conditions of 134°C at 0.2 MPa (n=5 per group at 0, 5, 50, and 100 hours). Percentage of total transmittance of light (T t %) of each specimen was measured using a spectrophotometer with an integrating sphere. X-ray diffraction analyses were used to measure tetragonal-monoclinic phase transformation. Surfaces were examined by scanning electron microscopy and energy dispersive spectrometry. Data were analyzed using 2-way ANOVA followed by the Tukey test (α=.05). The T t % ranged from 6.5% to 28.3%. Group LDLT obtained significantly higher transmittance than other tested groups, whereas groups KST and KUT had significantly higher T t % than groups BA and LPHT (Phydrothermal treatment for all tested translucent zirconias and a lithium disilicate glass-ceramic control. Hydrothermal treatment had minimal effects on the translucency of translucent zirconias. The tetragonal-monoclinic phase transformation rate of translucent zirconias was found to be low, except in group LPHT. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  4. Bulk and Interface Thermodynamics of Calcia-, and Yttria-doped Zirconia Ceramics: Nanograined Phase Stability

    Science.gov (United States)

    Drazin, John Walter

    while simultaneously collecting the energetic contribution of the adsorbing water vapor. With this data and apparatus, I have derived a 2nd order differential equation that relates the surface energy to the measured quantities such that I collected surfaces energies for over 35 specimens in the calcia-zirconia and yttria-zirconia systems for the first time. From the results, it was found that the monoclinic polymorph had the largest surface energy in the range of 1.9 - 2.1 ( J/m2) while the tetragonal surface energies were roughly 1.4 - 1.6 (J/m2), the cubic surface energies were roughly 0.8 - 1.0 (J/m2), and the amorphous surface energies were the smallest at roughly 0.7 - 0.8 (J/m 2). With the measured surface energy data, collected for the first time, we can create a nano-grain phase diagram similar to a bulk phase diagram that shows the stable polymorph as a function of dopant concentration and grain size using the bulk enthalpy data collected from high temperature oxide melt drop solution calorimetry. The phase diagrams show that pure zirconia will transform into tetragonal and cubic polymorphs from the monoclinic one at 7 and 5 nm respectively which confirms the experimental observations. The results are powerful predictive tools successfully applied in the nCZ and nYZ systems to a high degree of accuracy and adds a new development to conventional bulk phase diagrams. These diagrams should be the basis for nanotechnological efforts in nCZ and nYZ based systems, and suggest similar efforts are needed in other nano systems to pursue an in depth understanding and optimization of nanomaterials. After working on the theoretical aspects of phase stability, the focus of the research will shift to producing dense samples to measure observable quantities such as oxygen conduction and mechanical hardness. However, producing said samples with the nanocrystalline grain sizes has also been challenging as conventional sintering requires high temperatures which, as a consequence

  5. Response of MC3T3-E1cells on microroughen bioactive glass coated zirconia

    Directory of Open Access Journals (Sweden)

    Sapna Laxmi Tuladhar

    2017-10-01

    Full Text Available Background & Objectives:The objective of this study was to determine the cellular response of micro-roughened bioactive glass coated zirconia substrate (ZBR and non roughen bioactive glass coated zirconia substrate (ZB, and compare them with uncoated zirconia substrate (Z.  Materials & Methods:Surface micro-roughening was obtained using an Al2O3 sandblasting method. Abrasive blasting of zirconia coated bioactive glass produced an irregular finish with surface roughness average Ra 0.85 µm as determined by profilometer and scan electron microscope. Surface roughness of the samples in ascending order was ZBR>ZB>Z. Murine derived preosteoblast (MC3T3-E1 cells were seeded on the samples, and the cell morphology, growth, differentiation, were observed. Cell morphology was evaluated by means of scanning electron microscope (SEM, while cell proliferation and differentiation using MTT (3-(4,5-Dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide test and alkaline phosphates activity respectively. Results:The cell growth on all the samples continual increase with culturing up to 5days, showing good cell viability. However, there was no significant difference (p>0.05 with respect to the Z, ZB, and ZBR at day 5 at MTT assay. In particular, the alkaline phosphatase (ALP activity of the cells was significantly higher on the ZB and ZBR than Z samples at both 7 and 14 days.   Conclusion:Our findings demonstrate that bioactive glass coated surface was found to have better surface conditions to regulate bone cell differentiation 

  6. Ag nanoparticle-coated zirconia for antibacterial prosthesis.

    Science.gov (United States)

    Yamada, Risa; Nozaki, Kosuke; Horiuchi, Naohiro; Yamashita, Kimihiro; Nemoto, Reina; Miura, Hiroyuki; Nagai, Akiko

    2017-09-01

    Bacterial adhesion to dental materials is a major cause of caries and periodontitis, necessitating the development of compounds such as yttria-stabilized zirconia (YSZ) and silver nanoparticles (AgNPs), which are widely employed in medicine due to their high antimicrobial activity and low cytotoxicity. The main goal of this study is the synthesis of the broad antimicrobial activity of AgNP-coated YSZ with facile methods. The bactericidal AgNPs were immobilized on the surface of YSZ and tested for bactericidal activity against Staphylococcus aureus, Streptococcus mutans, Escherichia coli, and Aggregatibacter actinomycetemcomitans based on ISO 22196:2007. The loading of AgNPs was optimized by culturing mouse fibroblast cells on AgNP-coated YSZ with cell viability test based on ISO 10993-5. In addition, the silver release profile of AgNP-coated YSZ in artificial saliva was determined using an accelerated aging test. Antibacterial activity, and cell viability test revealed optimum performance with no cytotoxicity at a level of 32 μg/cm 2 . Accelerated aging test showed that the AgNP-coated surface was extremely stable, exhibiting a total silver leaching level of only 1% and confirming the effectiveness of this coating method for retaining AgNPs while exerting an antibacterial effect against oral pathogens. This finding also implies that the bactericidal action of AgNP-coated YSZ is not mediated by the released Ag ions, but rather corresponds to contact killing. Yttria-stabilized zirconia, YSZ; silver nanoparticles, AgNPs; field emission scanning electron microscopy, FE-SEM; X-ray photoelectron spectroscopy, XPS; grazing incidence X-ray diffraction, GIXRD; ultraviolet-visible, UV-vis; inductively coupled plasma atomic emission spectrometry, ICP-AES. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Platelet-Rich Blood Derivatives for Stem Cell-Based Tissue Engineering and Regeneration

    NARCIS (Netherlands)

    Masoudi, E.A.; Ribas, J.; Kaushik, G.; Leijten, Jeroen Christianus Hermanus; Khademhosseini, A.

    2016-01-01

    Platelet-rich blood derivatives have been widely used in different fields of medicine and stem cell-based tissue engineering. They represent natural cocktails of autologous growth factors, which could provide an alternative for recombinant protein-based approaches. Platelet-rich blood derivatives,

  8. Influence of multimode universal adhesives and zirconia primer application techniques on zirconia repair.

    Science.gov (United States)

    Seabra, Bruno; Arantes-Oliveira, Sofia; Portugal, Jaime

    2014-08-01

    More information is needed on the efficacy of the new universal adhesives and on the best 10-methacryloyloxydecyl dihydrogen phosphate- (MDP)-containing primer protocol to promote adhesion to zirconia. The aim of this study was to evaluate the influence of 2 new multimode MDP-containing adhesives and several application protocols of a zirconia primer on the shear bond strength (SBS) of composite resin to zirconia. Sixty zirconia (3Y-TZP) blocks were abraded (50 μm Al2O3) and divided into 6 experimental groups (n=10): one Z-Prime Plus coat without light polymerization; one Z-Prime Plus light-polymerized coat; two Z-Prime Plus coats without light polymerization; two Z-Prime Plus light-polymerized coats; All-Bond Universal; and ScotchBond Universal Adhesive. Multimode adhesives were applied according to the manufacturers' recommendations. After composite resin (Filtek Z250) light polymerization, the specimens were stored in distilled water (37°C/48 hours) and tested in shear (1 mm/min). Failure mode was classified as adhesive or mixed. Statistical analysis of the SBS data was performed with 1-way ANOVA followed by the Student-Newman-Keuls post hoc tests. Nonparametric tests (Kruskal-Wallis) were used to analyze the failure mode data (α=.05). The ScotchBond Universal Adhesive, All-Bond Universal, and two Z-Prime Plus light-polymerized coats groups showed a higher mean SBS than the other experimental groups (Padhesive failures. The new multimode adhesives tested were effective in promoting adhesion between composite resin and zirconia. Z-Prime Plus should be applied in 2 light-polymerized coats to promote SBS values similar to those of the new multimode adhesives. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  9. Fracture and Fatigue Resistance of Cemented versus Fused CAD-on Veneers over Customized Zirconia Implant Abutments.

    Science.gov (United States)

    Nossair, Shereen Ahmed; Aboushelib, Moustafa N; Morsi, Tarek Salah

    2015-01-05

    To evaluate the fracture mechanics of cemented versus fused CAD-on veneers on customized zirconia implant abutments. Forty-five identical customized CAD/CAM zirconia implant abutments (0.5 mm thick) were prepared and seated on short titanium implant abutments (Ti base). A second scan was made to fabricate 45 CAD-on veneers (IPS Empress CAD, A2). Fifteen CAD-on veneers were cemented on the zirconia abutments (Panavia F2.0). Another 15 were fused to the zirconia abutments using low-fusing glass, while manually layered veneers served as control (n = 15). The restorations were subjected to artificial aging (3.2 million cycles between 5 and 10 kg in a water bath at 37°C) before being axially loaded to failure. Fractured specimens were examined using scanning electron microscopy to detect fracture origin, location, and size of critical crack. Stress at failure was calculated using fractography principles (alpha = 0.05). Cemented CAD-on restorations demonstrated significantly higher (F = 72, p CAD-on and manually layered restorations. Fractographic analysis of fractured specimens indicated that cemented CAD-on veneers failed due to radial cracks originating from the veneer/resin interface. Branching of the critical crack was observed in the bulk of the veneer. Fused CAD-on veneers demonstrated cohesive fracture originating at the thickest part of the veneer ceramic, while manually layered veneers failed due to interfacial fracture at the zirconia/veneer interface. Within the limitations of this study, cemented CAD-on veneers on customized zirconia implant abutments demonstrated higher fracture than fused and manually layered veneers. © 2014 by the American College of Prosthodontists.

  10. Sem analysis zirconia-ceramic adhesion interface

    Science.gov (United States)

    CARDELLI, P.; VERTUCCI, V.; MONTANI, M.; ARCURI, C.

    2015-01-01

    SUMMARY Objectives Modern dentistry increasingly tends to use materials aesthetically acceptable and biomimetic. Among these are zirconia and ceramics for several years, a combination that now has becoming synonym of aesthetic; however, what could be the real link between these two materials and especially its nature, remains a controversial topic debated in the literature. The aim of our study was to “underline” the type of bonding that could exist between these materials. Materials and methods To investigate the nature of this bond we used a SEM microscopy (Zeiss SUPRA 25). Different bilaminar specimens: “white” zirconia Zircodent® and ceramic “Noritake®”, after being tested with loading test in bending (three-point-bending) and FEM analysis, were analyzed by SEM. Fragments’ analysis in closeness of the fracture’s point has allowed us to be able to “see” if at large magnifications between these two materials, and without the use of linear, could exist a lasting bond and the possible type of failure that could incur. Results From our analysis of the specimens’ fragments analyzed after test Equipment, it is difficult to highlight a clear margin and no-adhesion zones between the two materials, although the analysis involving fragments adjacent to the fracture that has taken place at the time of Mechanical test Equipment. Conclusions According to our analysis and with all the clarification of the case, we can assume that you can obtain a long and lasting bond between the zirconia and ceramics. Agree to the data present in the literature, we can say that the type of bond varies according to the type of specimens and of course also the type of failure. In samples where the superstructure envelops the ceramic framework Zirconium we are in the presence of a cohesive failure, otherwise in a presence of adhesive failure. PMID:27555905

  11. Thermal conductivity of zirconia thermal barrier coatings

    Science.gov (United States)

    Dinwiddie, R. B.; Beecher, S. C.; Nagaraj, B. A.; Moore, C. S.

    1995-01-01

    Thermal barrier coatings (TBC's) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBC's is of primary importance. Physical vapor deposition (PVD) and plasma spraying (PS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The PS coatings were applied with either standard powder or hollow sphere particles. The hollow sphere particles yielded a lower density and lower thermal conductivity coating. The thermal conductivity of both fully and partially stabilized zirconia, before and after thermal aging, will be compared. The thermal conductivity of the coatings permanently increases upon exposed to high temperatures. These increases are attributed to microstructural changes within the coatings. Sintering of the as-fabricated plasma sprayed lamellar structure is observed by scanning electron microscopy of coatings isothermally heat treated at temperatures greater than 1100 C. During this sintering process the planar porosity between lamella is converted to a series of small spherical pores. The change in pore morphology is the primary reason for the observed increase in thermal conductivity. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the PVD coatings are less susceptible to thermal aging effects, preliminary results suggest that they have a higher thermal conductivity than PS coatings, both before and after thermal aging. The increases in thermal conductivity due to thermal aging for partially stabilized plasma sprayed zirconia have been found to be less than for fully stabilized plasma sprayed zirconia coatings. The high temperature thermal diffusivity data indicate that if these coatings reach a temperature above 1100 C

  12. Studies of alumina additions in zirconia - magnesia

    International Nuclear Information System (INIS)

    Muccillo, R.

    1987-01-01

    Ionic conductivity measurements have been carried out in the 500 0 C - 1000 0 C temperature range in Mg - PSZ (Partially Stabilized Zirconia) with 0.5 to 10 mol % alumina additions. All specimens were prepared by pressing followed by pre - and sintering at 1000 0 C/2h and1450 0 C/4h, respectively. Thermal histerysis of the ionic conductivity have been detected, probably due to phase changes in the Mg-PSZ samples. The results show that alumina additions up to 2.1% enhances densification with no major variations in electrical resistivity values. (Author) [pt

  13. synthesis of schiff bases derived from 2-hydroxy-1-naphth

    African Journals Online (AJOL)

    119 ppm). KEY WORDS: Schiff base, ... antimicrobial agents owing to their low toxicity, low cost and excellent activity against bacterial diseases. ..... antimicrobial activity and crystal structure of silver and copper complexes of sulfamethazine.

  14. Investigation of phase stability in the scandia-zirconia

    International Nuclear Information System (INIS)

    Grosso, Robson Lopes

    2016-01-01

    In this work, the phase stability of scandia-zirconia (ScSZ) system was investigated by the thermodynamic study of nanoparticles, within the range of 0 to 20 mol% Sc 2 O 3 , and by codoping of ZrO 2 -10 mol% Sc 2 O 3 (10ScSZ) with Dy 2 O 3 and Nb 2 O 5 . The phase stability of ScSZ was evaluated based on thermodynamic data collected by water adsorption microcalorimetry and high temperature oxide melt solution. Nanostructured zirconia-scandia solid solutions were synthesized by coprecipitation method. Thermodynamic data were determined for ScSZ polymorph (monoclinic, tetragonal, cubic, rhombohedral β and γ) found by X-ray diffraction. This systemic work resulted in an unprecedented phase diagram at the nanoscale of particle size-composition. The effects of additives on 10ScSZ were investigated aiming to stabilize the cubic (c) structure at room temperature and to suppress the characteristic cubic-rhombohedral β phase transformation. Compositions were prepared by coprecipitation and solid state reaction. Materials were sintered by conventional and spark plasma sintering. Full stabilization of the cubic phase was attained by 1 mol% Dy 2 O 3 and 0.5 mol% Nb 2 O 5 additions. The smallest Nb 2 O 5 content required for cubic phase stabilization was attributed to liquid phase formation during sintering and to small ionic radius of Nb 5+ . Results of high temperature X-ray diffraction and thermal analysis show suppression of the c-β transformation. Samples containing 0.5 mol% Nb 2 O 5 show total ionic conductivity similar to 10ScSZ without additives within a broad temperature range with high stability during 170 h at 600 °C. (author)

  15. The effect of zirconia on flexural strength of IPS Empress 2 ceramic

    Directory of Open Access Journals (Sweden)

    Kermanshah H

    2007-06-01

    Full Text Available Background and Aim: All ceramic, inlay-retained resin bonded fixed partial denture is a conservative method for replacement of missing teeth, because of minimal tooth reduction. The connector between the retainer and the pontic is the weak point of these bridges. Reinforcement of ceramic core will increase the clinical longevity. The aim of this study was to determine the effect of zirconia on flexural strength of IPS Empress 2 core ceramic.Materials and Methods: In this experimental in vitro study, twenty eight bar shape specimens (17´3.1´3.1 mm were made of four different materials: (1 Slip casting in-ceram alumina core (control group (2 Hot-pressed lithium disilicate core ceramic (IPS Empress 2 (3 IPS Empress 2 with cosmopost (zirconia post inserted longitudinally in the center of the bar (4 IPS Empress 2 with cosmopost (zirconia post inserted longitudinally in bottom of the bar. Specimens were subjected to three-point flexure loading with the span of 15mm, at a cross-head speed of 0.5 mm/min. Failure loads were recorded and analyzed using one-way ANOVA and Tomhane Post-hoc tests and p<0.05 was set as the level of significance. Fractured surfaces were then observed by scanning electron microscope (SEM. Four additional samples were made as the third group, and zirconia-IPS interface was observed by SEM before fracture.Results: Mean values and standard deviations of three point flexural strengths of groups 1 to 4, were: 378.4±44.6, 258.6±27.5, 144.3±51.7, 230±22.3 MPa respectively. All the groups were statistically different from each other (P<0.05, except groups 2 and 4. The flexural strengths of groups 2, 3, 4 were significantly lower than group 1. Group 3 had the lowest flexural strength. SEM analysis showed that the initiated cracks propagated in the interface of zirconia post and IPS Empress 2 ceramic.Conclusion: Based on the results of this study, inserting zirconia post (cosmopost in IPS Empress 2 ceramic does not reinforce all

  16. Chemical treatment and biomimetic coating evaluating in zirconia-alumina ceramics

    International Nuclear Information System (INIS)

    Aguiar, Amanda Abati

    2007-01-01

    Ceramic materials, as alumina and zirconia have been explored along the years as biomaterials application. The bio inert nature has been stimulating the development of new alternatives, as chemical treatments to improve the biological application of these ceramics. The biomimetic process of bio inert ceramics for coating apatite is based on soaking the implant in a simulated body fluid, SBF, with ion concentrations nearly equal to those of human blood plasma. The bioactivity of the material is related with the formation of a layer constituted of hydroxyapatite low crystalline, similar to the biological apatite. The biocompatibility associated to the structural properties of the alumina and zirconia has been stimulating the clinical use of these materials, mainly in areas of larger mechanical requests, places not recommended for bioactive hydroxyapatite, for instance. In this work samples of alumina, zirconia doped with Yttria (3% mol) and composites of alumina and zirconia doped with Yttria (3% mol) were prepared by co-precipitation method, calcinate, sintered, chemically treated with solutions of acid phosphoric and sodium hydroxide and them immersed in 1.0 M and 1.5 M SBF. The calcinate powders were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), gas adsorption (BET) and laser diffraction. The XRD results indicate that the samples are low crystalline. It was observed for BET that the samples present high specific surface area. The results of laser diffraction and SEM showed that the powders are agglomerates. The sintered samples were analyzed by XRD, SEM and X-ray fluorescence (XRF). The phases quantified by Rietveld method were: cubic, tetragonal and monoclinic of the zirconia, besides the phase alpha of the alumina. The chemical treatment with phosphoric acid didn't present a tendency of larger apatite formation in relation to the samples no chemically treated. The treatment with sodium hydroxide provoked accentuated transformation of

  17. Using Dark Field X-Ray Microscopy To Study In-Operando Yttria Stabilized Zirconia Electrolyte Supported Solid Oxide Cell

    DEFF Research Database (Denmark)

    Sierra, J. X.; Poulsen, H. F.; Jørgensen, P. S.

    Dark Field X-Ray Microscopy is a promising technique to study the structure of materials in nanometer length scale. In combination with x-ray diffraction technique, the microstructure evolution of Yttria Stabilized Zirconia electrolyte based solid oxide cell was studied running at extreme operati...

  18. Densification of zirconia films by coevaporation with silica

    International Nuclear Information System (INIS)

    Feldman, A.; Farabaugh, E.N.

    1985-04-01

    Optical films of zirconia have been receiving considerable attention because of their potential use as the high-index layer in multilayer optical coatings for the ultraviolet portion of the spectrum. Several problems are associated with electron-beam deposited zirconia films, including index instability and index inhomogeneity. The index instability is caused by the adsorption and the desorption of water in the porous columnar structure of the zirconia films. Index inhomogeneity is due to the inhomogeneous structure in the films. Recent work has shown that the first several tens of nanometers of a film possess a cubic structure, whereas the outmost layers possess a monoclinic structure. One approach for producing bulk-like zirzonia films that is receiving considerable attention at present is ion-assisted electron-beam deposition. This is because the method has successfully produced zirconia films having bulk-like densities and refractive indices that show insignificant sensitivity to water adsorption. In this paper a similar effect is demonstrated when mixed zirconia:silica films are produced by coevaporation from independent electron-beam sources, and, in particular, it is shown that the admixture of a small amount of silica with the zirconia produces a film possessing a higher refractive index than a pure zirconia film

  19. [Effects of colorants on yttria stabilized tetragonal zirconia polycrystals powder].

    Science.gov (United States)

    Wang, Bo; Chen, Jianfeng; Zhang, Yanchun; Wang, Ru

    2015-10-01

    To evaluate the effect of Fe2O3 and CeO2 as colorants on yttria stabilized tetragonal zirconia poly-crystals (Y-TZP) powder. The spray granulation slurry of colored zirconia was prepared with different concentrations of Fe2O3 (0.15%) and CeO2 (4%), which were added in Y-TZP. Zirconia powder was made by spray granulation. The powder specimens were divided into three groups: uncolored zirconia, Fe2O3 (0.15%) zirconia, and CeO2 (4%) zirconia. The particle morphologies of the powder specimens were measured with a laser particle size analyzer and an optical microscope. The differences in D50 among the three groups were statistically significant (PCeO2 and uncolored zirconia (PCeO2 (P>0.05). Mostly spherical powder was observed in the three groups. Fe2O3 as a colorant can affect particles, whereas CeO2 has no effect.

  20. Lithium and sodium incorporation in zirconia: a spectroscopic study

    International Nuclear Information System (INIS)

    Bender, Alexandra

    2001-01-01

    Zircaloy is used as fuel cladding material. Lithium dissolved in the cooling water enhances its corrosion and incorporates into the oxide layer. It could substitute for zirconium atoms forming a solid solution or modify crystallographic structure of zirconia. The aim of this work is to determine the crystallographic structure and the local environment of dopant in Li and Na doped zirconia samples obtained by ionic implantation and coprecipitation route, and then to discuss their interest in term of 'lithium effect study'. Implanted zirconia samples are constituted by metallic aggregates oxidised at their surface. A third 'Na 2 ZrO 3 ' local environment has been detected probably due to Na dissolved in zirconia. An experimental procedure has been developed allowing Li and Na doping by a coprecipitation route. Lithium and sodium hydroxide helps the stabilisation of metastable zirconia. Stabilisation doesn't seem to be due to alkaline substitution for zirconium but it must be connected to the effect of both alkaline hydroxides on the first precipitation steps. Similarities between Li doped zirconia by coprecipitation route and zirconia obtained by oxidation of zirconium in the presence of LiOH should help to understand the so-called 'lithium effect'. Finally sodium seems to be relevant to simulate lithium when samples are elaborated and studied at room temperature. It is not the case for annealed samples. (author) [fr

  1. Fracture Load Before and After Veneering Zirconia Posterior Fixed Dental Prostheses.

    Science.gov (United States)

    Rodríguez, Verónica; Castillo-Oyagüe, Raquel; López-Suárez, Carlos; Gonzalo, Esther; Peláez, Jesús; Suárez-García, María-Jesús

    2016-10-01

    To evaluate the fracture load of 3-unit zirconia-based posterior fixed dental prostheses (FDPs) before and after veneering the frameworks. Forty standardized stainless-steel master dies were fabricated (height: 5 mm, convergence: 6º, chamfer: 1 mm) and randomly screwed in pairs onto metal bases. The bases were randomly divided into two groups (n = 20 each) according to the zirconia CAD/CAM system used for constructing 3-unit structures for FDPs: group 1 (L): Lava All-ceramic, group 2 (Z): IPS e.max ZirCAD. Half of the zirconia structures per group were randomly selected and veneered, while the remaining half was left unveneered. The specimens were luted in standard fashion onto the stainless steel master dies using conventional glass ionomer cement. All specimens were tested for fracture load (FL). Specimens were subjected to a three-point bending test until fracture by applying an axial compressive load at the central fossa of the pontics with a universal testing machine at a 0.5 mm/min crosshead speed. Wilcoxon's rank-sum test and Weibull statistics were used for statistical analysis (α = 0.05). L structures recorded significantly higher values of load to fracture than the Z group both before and after veneering. Within each ceramic group, no differences were found between unveneered and veneered frameworks. Although further studies are necessary to corroborate these findings, both zirconia systems could be recommended for restoring posterior teeth on the basis of the fracture load values recorded in this experiment (>1000 N). The veneering procedure did not affect the overall load to fracture in any group. © 2015 by the American College of Prosthodontists.

  2. Effects of superplastic deformations on thermophysical properties of tetragonal zirconia polycrystals

    International Nuclear Information System (INIS)

    Motohashi, Y.; Wan, C.; Sakuma, T.; Harjo, S.; Shibata, T.; Ishihara, M.; Baba, S.; Hoshiya, T.

    2004-01-01

    Neutron irradiation studies on superplastic zirconia-based ceramics are now in progress as an innovative basic project using the High-temperature Engineering Test Reactor (HTTR) in Japan. The characteristics of the zirconia-based engineering components, made through the formation of superplastic, may be strongly affected by their response to transient or steady-state heat flow. Reliable thermophysical properties such as the coefficients of thermal expansion and thermal conductivity are, therefore, needed to estimate and predict the influence of a high-temperature environment. Accordingly, one of this project's targets is to study the thermophysical properties of superplastic zirconia-based ceramics. The first stage of the research addresses the effects of superplastic deformations on the thermophysical properties of a typical superplastic ceramic, 3 mol% yttria-stabilised tetragonal zirconia polycrystals (3Y-TZP), in its un-irradiated state. First, superplastic tensile deformations were conducted on 3Y-TZP specimens under different conditions in order to obtain specimens with different microstructural characteristics. Afterwards, the following actions were taken: - Specific heat measurements were conducted on the specimens at temperatures ranging from 473 K to 1273 K. - The thermal diffusivity was measured using a laser flash method. The thermal conductivity was then calculated from the measured thermal diffusivity, specific heat and density. - The linear thermal expansion was measured by a push-rod type dilatometer from 300 K to 1473 K. The coefficient of linear thermal expansion (CTE) was estimated from the thermal expansion data. The results obtained from the above measurements are discussed, as is the microstructural evolution caused by the superplastic deformations. It was found that the specific heat was almost independent of microstructural evolution, whereas the thermal diffusivity, thermal conductivity and thermal expansion were quite sensitive to

  3. Eco friendly nitration of toluene using modified zirconia

    Directory of Open Access Journals (Sweden)

    K.R. Sunaja Devi

    2013-03-01

    Full Text Available Nitration of toluene has been studied in the liquid phase over a series of modified zirconia catalysts.  Zirconia, zirconia- ceria (Zr0.98Ce0.02O2, sulfated zirconia and sulfated zirconia- ceria were synthesised by co precipitation method and were characterised by X-ray diffraction, BET surface area, Infra red spectroscopy analysis (FTIR, Thermogravimetric analysis (TGA, Scanning Electron Microscopy (SEM and Energy Dispersive X ray analysis (EDAX. The acidity of the prepared catalysts was determined by FTIR pyridine adsorption study. X-ray diffraction studies reveal that the catalysts prepared mainly consist of tetragonal phase with the crystallite size in the nano range and the tetragonal phase of zirconia is stabilized by the addition of ceria. The modified zirconia samples have higher surface area and exhibits uniform pore size distribution aggregated by zirconia nanoparticles. The onset of sulfate decomposition was observed around 723 K for sulfated samples. The catalytic performance was determined for the liquid phase nitration of toluene to ortho-, meta- and para- nitro toluene. The effect of reaction temperature, concentration of nitric acid, catalyst reusability and reaction time was also investigated. © 2013 BCREC UNDIP. All rights reservedReceived: 20th November 2012; Revised: 8th December 2012; Accepted: 7th January 2013[How to Cite: K. R. S. Devi, S. Jayashree, (2013. Eco friendly nitration of toluene using modified zirconia. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (3: 205-214. (doi:10.9767/bcrec.7.3.4154.205-214][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.7.3.4154.205-214 ] View in  |

  4. Fabrication and Characterization of Dual Phase Magnesia-Zirconia Ceramics Doped with Plutonia

    Energy Technology Data Exchange (ETDEWEB)

    P. G. Medvedev; J. F. Jue; S. M. Frank; M.K. Meyer

    2005-05-01

    Dual phase magnesia-zirconia ceramics doped with plutonia are being studied as an inert matrix fuel (IMF) for light water reactors. The motivation of this work is to develop an IMF with a thermal conductivity superior to that of the fuels based on yttria stabilized zirconia. The concept uses the MgO phase as an efficient heat conductor to increase thermal conductivity of the composite. In this paper ceramic fabrication and characterization by scanning electron microscopy, energy and wavelength dispersive xray spectroscopy is discussed. Characterization shows that the ceramics consist of the two-phase matrix and PuO2-rich inclusions. The matrix is comprised of pure MgO phase and MgO-ZrO2-PuO2 solid solution. The PuO2-rich inclusion contained dissolved MgO and ZrO2.

  5. Development of a High Temperature Heater using an Yttria Stabilized Zirconia Cored Brick Matrix

    Science.gov (United States)

    Smith, K. W.; Decoursin, D. G.

    1971-01-01

    The Ames pilot heater is a ceramic regenerative heater that provides high temperature air for aerodynamic and combustion experiments. The development of this heater to provide a heat storage bed with temperature capability of about 4600 R is described. A bed was designed and installed having cored brick elements of yttria-stabilized zirconia. The bed dimensions were 14 inches in diameter by 10 feet high. The thermal stress limitations of the bed were studied and maximum air flow rates based upon these limits were established. A combustion reheat system was designed and installed to provide the necessary control over the bed temperature distribution. The revised heater system was successfully operated at a maximum bed temperature of 4600 R. The successful operation demonstrated that yttria-stabilized zirconia cored brick can satisfy the high temperature-long duration requirement for storage heater applications.

  6. High energy milling of zirconia-titania powders synthesized by coprecipitation

    International Nuclear Information System (INIS)

    Silva, Cristiano M.B.; Marchi, Juliana; Lazar, Dolores R.R.; Ussui, Valter

    2009-01-01

    Zirconia based ceramics are known by its remarkable mechanical properties as hardness and fracture toughness and in biomedical applications are classified as bioinert. By its turn, titania ceramics has been studied due to its ability to bond directly to bone tissue, but are structurally brittle. Properties of ceramics are strongly dependent of physical and chemical characteristics of its former powders. In the present work, research done for the synthesis of zirconia-titania ceramics by the coprecipitation route are presented, emphasizing the conditioning process through a high energy milling in a atritor mill, classifying of powders in vibratory sieves and forming of cylindrical ceramic samples followed by a sintering process at 1500 deg C for 01 hour. The intermediary samples produced in the various steps of the process were characterized by scanning electronic microscope, X-ray diffraction, nitrogen gas adsorption and granulometric analysis. (author)

  7. Overview description of the base scenario derived from FEP analysis

    International Nuclear Information System (INIS)

    Locke, J.; Bailey, L.

    1998-01-01

    This report forms part of a suite of documents describing the Nirex model development programme. The programme is designed to provide a clear audit trail from the identification of significant features, events and processes (FEPs) to the models and modelling processes employed within a detailed performance assessment. A scenario approach to performance assessment has been adopted. It is proposed that potential evolutions of a deep geological radioactive waste repository can be represented by a base scenario and a number of variant scenarios. It is intended that assessment of the base scenario would form the core of any future performance assessment. The base scenario is chosen to be broad-ranging and to represent the natural evolution of the repository system and its surrounding environment. The base scenario is defined to include all those FEPs which are certain to occur and those which are judged likely to occur for a significant period of the assessment - timescale. Variant scenarios are defined by FEPs which represent a significant perturbation to the natural system evolution, for example the occurrence of a large seismic event. The structuring of FEPs on a Master Directed Diagram (MDD), provides a systematic framework for identifying those FEPs which form part of the natural evolution of the system and those which may define alternative potential evolutions of the repository system. In order to construct a description of the base scenario, FEPs have been grouped into a series of conceptual models. Conceptual models are groups of FEPs, identified from the MDD, representing a specific component or process within the disposal system. It has been found appropriate to define conceptual models in terms of the three main components of the disposal system: the repository engineered system, the surrounding geosphere and the biosphere. For each of these components, conceptual models provide a description of the relevant subsystem in terms of its initial characteristics

  8. and O-based composite materials derived from differential ...

    Indian Academy of Sciences (India)

    available values. It was also observed that for each of these samples, Zeff was almost a constant at the three energies which unambiguously justified the conclusions drawn by other authors earlier [Manjunathaguru and ... with a personal computer-based multichannel analyzer. The counts under the peak were determined ...

  9. A tool to ascertain taxonomic relatedness based on features derived ...

    Indian Academy of Sciences (India)

    MADHU

    placements of a new isolate based on phenotypic characteristics are now being supported by information preserved in the 16S rRNA gene. ... were extracted from the training data set of the 16S rDNA sequence, and was subjected to an artificial neural network ..... variables to 275 principal components, accounting for 99%.

  10. Characterization of Schiff base derived from 2-hydroxo-1 ...

    African Journals Online (AJOL)

    Molar conductance measurements showed that the complex is non electrolyte with very high stability constant value. Gibb's free energy determination showed that the complex is very stable as shown in the high decomposition temperature measurements. Keywords: Potentiometry, Schiff base, Spectrophotometry, Stability ...

  11. synthesis of schiff bases derived from 2-hydroxy-1-naphth

    African Journals Online (AJOL)

    Amino acids have importance in Schiff base complexes formation in which these can act as ligands due to their physiological and pharmacological activities. ..... Aromatic carbon attached with azomethine Nitrogen. Aliphatic. Carbon. Aromatic carbon attached with azomethine Carbon. HNLH. 171.81. 158.84. 122.00. 40.33.

  12. Deriving tolerant grammars from a base-line grammar

    NARCIS (Netherlands)

    A.S. Klusener (Steven); R. Lämmel (Ralf)

    2003-01-01

    textabstractA grammar-based approach to tool development in re- and reverse engineering promises precise structure awareness, but it is problematic in two respects. Firstly, it is a considerable up-front investment to obtain a grammar for a relevant language or cocktail of languages. Existing work

  13. Isomerization-cracking of n-octane on catalysts based on heteropolyacid H{sub 3}Pw{sub 12}O{sub 40} and heteropolyacid supported on zirconia and promoted with Pt and Cs

    Energy Technology Data Exchange (ETDEWEB)

    Manuele, Debora L.; Torres, Gerardo C.; Benitez, Viviana M.; Badano, Juan M.; Yori, Juan C.; Sepulveda, Jorge H., E-mail: jsepulve@fiq.unl.edu.ar [Universidad Nacional de Litoral, Santa Fe (Argentina). Instituto de Investiaciones en Catalisis y Petroquimica. Consejo Nacional de Investigaciones Cientificas y Tecnicas

    2013-10-01

    Isomerization-cracking of n-octane was studied using H{sub 3}PW{sub 12}O{sub 40} (HPA) and HPA supported on zirconia and promoted with Pt and Cs. The addition of Pt and Cs to the supported HPA did not modify the Keggin structure. The Pt addition to the supported HPA did not substantially modify the total acidity; however, the Broensted acidity increased significantly. Cs increased the total acidity and Broensted acidity. A linear relation was observed between the n-C{sub 8} total conversion and Broensted acidity. The most adequate catalysts for performing isomerization and cracking to yield high research octane number (RON) are those with higher values of Broensted acidity. (author)

  14. Activity measurement of Ga in liquid Ga-Pb alloys by EMF method with zirconia solid electrolyte

    Directory of Open Access Journals (Sweden)

    Katayama I.

    2002-01-01

    Full Text Available EMF measurement of the electrochemical cell with zirconia as solid electrolyte was performed to determine the gallium activity from 950 to 1150K in the entire composition range of liquid Ga-Pb alloys. In the whole concentration range, activity of Ga shows moderately positive deviations from ideality, and activity of Pb which is derived by Gibbs- Duhem equation shows also positive deviation from ideality. These are compared with published data obtained by different experimental methods.

  15. Zirconia powders production by precipitation: state-of-art review

    International Nuclear Information System (INIS)

    Oliveira, Ana Paula Almeida de; Torem, Mauricio Leonardo

    1994-01-01

    The important role played by zirconia in advanced ceramics can be attributed to its excellent wear and corrosion resistance and refractory character. The polymorphic nature of zirconia made the controlled addition of stabilizing oxides or the constraining effect of a dense ceramics matrix necessary to maintain high parameters had a significant influence on powder properties and on compacted powder behaviour in sintering. Particle shape and size, purity and crystalline structure were specially influenced by precipitation parameters. Therefore, this work presented a review of the state of the art in zirconia powder production and in the recent research on precipitation of that powder. (author)

  16. Inhibition of surface bound carbonate stabilization of tetragonal zirconia

    DEFF Research Database (Denmark)

    Nielsen, Mette Skovgaard; Almdal, Kristoffer; Lelieveld, A. van

    2011-01-01

    Water is known to initiate a tetragonal to monoclinic phase transformation in zirconia particles. Carbonates on the zirconia surface react with water molecules and hence reduce the transformation rate. This study investigates the possibility of inhibition of the reaction between surface carbonates...... and water in order to increase the transformation rate in the zirconia crystals. It was found possible to limit the reaction by reacting the surface carbonates with alcohols, a thiol and a primary amide prior to reaction with water. It was also concluded that di- and trialcohols are able to stabilize...

  17. Glass ceramic toughened with tetragonal zirconia

    Science.gov (United States)

    Keefer, Keith D.; Michalske, Terry A.

    1986-01-01

    A phase transformation-toughened glass ceramic and a process for making it are disclosed. A mixture of particulate network-forming oxide, network-modifying oxide, and zirconium oxide is heated to yield a homogeneous melt, and this melt is then heat-treated to precipitate an appreciable quantity of tetragonal zirconia, which is retained at ambient temperature to form a phase transformation-toughened glass ceramic. Nucleating agents and stabilizing agents may be added to the mixture to facilitate processing and improve the ceramic's properties. Preferably, the mixture is first melted at a temperature from 1200.degree. to 1700.degree. C. and is then heat-treated at a temperature within the range of 800.degree. to 1200.degree. C. in order to precipitate tetragonal ZrO.sub.2. The composition, as well as the length and temperature of the heat-treatment, must be carefully controlled to prevent solution of the precipitated tetragonal zirconia and subsequent conversion to the monoclinic phase.

  18. Cubic zirconia as a high-quality facet coating for semiconductor lasers

    Energy Technology Data Exchange (ETDEWEB)

    Chin, A.K.; Satyanarayan, A.; Zarrabi, J.H.; Vetterling, W.

    1988-08-01

    In this paper we describe the properties of high-quality, semiconductor laser facet coatings based on yttria-stabilizied cubic zirconia (90-m% ZrO/sub 2//10-m% Y/sub 2/O/sub 3/). We have found that cubic zirconia films can be reproducibly deposited by electron-beam evaporation with an index of refraction of 1.98 at 6328 A, almost ideal for use as a single-layer antireflection coating for GaAs/GaAlAs-based lasers. ZrO/sub 2/ has a monoclinic crystal structure at room temperature, but changes to tetragonal, hexagonal, and cubic phases upon heating to higher temperatures. However, the addition of the Y/sub 2/O/sub 3/ stabilizes ZrO/sub 2/ in the cubic form, thus allowing electron-beam deposition of thin films of this material to be more controllable and reproducible without the usual addition of oxygen into the vacuum chamber during deposition. Preliminary aging tests of high-power GaAs/GaAlAs lasers show that cubic zirconia films suppress the photo-enhanced oxidation of laser facets that degrades device performance.

  19. Human fetal osteoblast behavior on zirconia dental implants and zirconia disks with microstructured surfaces. An experimental in vitro study.

    Science.gov (United States)

    Delgado-Ruíz, Rafael Arcesio; Gomez Moreno, Gerardo; Aguilar-Salvatierra, Antonio; Markovic, Aleksa; Mate-Sánchez, Jose Eduardo; Calvo-Guirado, José Luis

    2016-11-01

    To measure the lateral surface area of microgrooved zirconia implants, to evaluate the cell geometry and cell density of human fetal osteoblasts seeded on zirconia microgrooved implants, to describe the surface roughness and chemistry, and to evaluate the activity of human fetal osteoblasts seeded on zirconia microgrooved disks. This experimental in vitro study used 62 zirconia implants and 130 zirconia disks. Two experimental groups were created for the implants: 31 non-microgrooved implants (Control) and 31 microgrooved implants (Test); two experimental groups were created for the disks: 65 non-microgrooved disks (Control) and 65 microgrooved disks (Test). The following evaluations of the implants were made: lateral surface area (LSA), cell morphology, and density of human fetal osteoblasts seeded on implant surfaces. On the disks, surface parameters (roughness and chemistry) and cell activity (alkaline phosphatase - ALP and alizarin red - ALZ) were evaluated at 7 and 15 days. LSA was lower for control implants (62.8 mm) compared with test implants (128.74 mm) (P zirconia implants with microgrooves. (ii) The LSA of microgrooved zirconia implants is greater and provides more available surface compared with implants of the same dimensions without microgrooves. (iii) Microgrooves on zirconia implants modify the morphology and guide the size and alignment of human fetal osteoblasts. (iv) Zirconia surfaces with microgrooves of 30 μm width and 70 μm separation between grooves enhance ALP and ALZ expression by human fetal osteoblasts. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  20. Analytical Derivation: An Epistemic Game for Solving Mathematically Based Physics Problems

    Science.gov (United States)

    Bajracharya, Rabindra R.; Thompson, John R.

    2016-01-01

    Problem solving, which often involves multiple steps, is an integral part of physics learning and teaching. Using the perspective of the epistemic game, we documented a specific game that is commonly pursued by students while solving mathematically based physics problems: the "analytical derivation" game. This game involves deriving an…

  1. Integrating ecological insight derived from individual-based simulations and physiologically structured population models

    NARCIS (Netherlands)

    Nisbet, R.M.; Martin, B.T.; de Roos, A.M.

    2016-01-01

    Two contrasting approaches are widely used to derive population dynamics as an emergent property deriving from the physiology and behavior of individual organisms. "Individual-based models" (IBMs) are computer simulations where the "state" (e.g., age, size) of each individual in a population is fol-

  2. Evaluation of Effect of Zirconia Surface Treatment, Using Plasma of Argon and Silane, on the Shear Bond Strength of Two Composite Resin Cements.

    Science.gov (United States)

    Kaimal, Aswathy; Ramdev, Poojya; Shruthi, C S

    2017-08-01

    Yttria stabilised tetragonal zirconia opens new vistas for all ceramic restoration by the mechanism of transformation toughening, making it much stronger compared to all other ceramic materials. Currently, it is the most recent core material for all ceramic fixed partial dentures due to its ability to withstand high simulated masticatory loads. Problems which have been reported with zirconia restorations involve the core cement interface leading to loss of retention of the prosthesis. Different reasons which have been reported for the same include the lack of adhesion between zirconia and commonly used cements due to absence of silica phase which makes zirconia not etchable. In addition, the hydrophobic nature of zirconia causes low wettability of zirconia surface by the adhesive cements which are commonly used. The purpose of this in vitro study was to compare and evaluate the effect of two pre-treatments of zirconia, using plasma of argon and silane, on the shear bond strength values of two composite resin cements to zirconia and to evaluate the failure pattern of the debonded areas using stereomicroscopic analysis. Sixty zirconia discs (10 mm×2 mm) were randomly divided into three groups (n=20), following surface treatment, with airborne particle abrasion, using 110 µm Al2O3: Group I (control), Group II (plasma of argon cleaning), and Group III (application of silane primer). Each group had two subgroups based on the type of resin cement used for bonding: subgroup A; Rely X Ultimate (3M ESPE) and subgroup B; Panavia F (Kuraray). In subgroup A, Rely X universal silane primer and in subgroup B Clearfil ceramic primer was used. Shear bond strengths were determined after water storage for one day and thermocycling for 5000 cycles. Data (megapascal) were analyzed using ANOVA and Bonferroni test. Specimens were subjected to stereomicroscopic analysis, for evaluation of failure pattern. Group III produced the highest shear bond strength followed by Group II and Group

  3. On the interfacial fracture of porcelain/zirconia and graded zirconia dental structures

    Science.gov (United States)

    Chai, Herzl; Lee, James J.-W; Mieleszko, Adam J.; Chu, Stephen J.; Zhang, Yu

    2014-01-01

    Porcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their susceptibility to fracture remains a practical problem. The failure of PFZ prostheses often involves crack initiation and growth in the porcelain, which may be followed by fracture along the porcelain/zirconia (P/Z) interface. In this work, we characterized the process of fracture in two PFZ systems, as well as a newly developed graded glass-zirconia structure with emphases placed on resistance to interfacial cracking. Thin porcelain layers were fused onto Y-TZP plates with or without the presence of a glass binder. The specimens were loaded in a four-point-bend fixture with the thin porcelain veneer in tension, simulating the lower portion of the connectors and marginal areas of a fixed dental prosthesis (FDP) during occlusal loading. The evolution of damage was observed by a video camera. The fracture was characterized by unstable growth of cracks perpendicular to the P/Z interface (channel cracks) in the porcelain layer, which was followed by stable cracking along the P/Z interface. The interfacial fracture energy GC was determined by a FEA taking into account stress shielding effects due to the presence of adjacent channel cracks. The resulting GC was well less than commonly reported values for similar systems. Fracture in the graded Y-TZP samples occurred by a single channel crack at a much greater stress than for PFZ. No delamination between the residual glass layer and graded zirconia occurred in any of the tests. Combined with its enhanced resistance to edge chipping and good esthetic quality, graded Y-TZP emerges as a viable material concept for dental restorations. PMID:24769152

  4. Flexural strength and the probability of failure of cold isostatic pressed zirconia core ceramics.

    Science.gov (United States)

    Siarampi, Eleni; Kontonasaki, Eleana; Papadopoulou, Lambrini; Kantiranis, Nikolaos; Zorba, Triantafillia; Paraskevopoulos, Konstantinos M; Koidis, Petros

    2012-08-01

    The flexural strength of zirconia core ceramics must predictably withstand the high stresses developed during oral function. The in-depth interpretation of strength parameters and the probability of failure during clinical performance could assist the clinician in selecting the optimum materials while planning treatment. The purpose of this study was to evaluate the flexural strength based on survival probability and Weibull statistical analysis of 2 zirconia cores for ceramic restorations. Twenty bar-shaped specimens were milled from 2 core ceramics, IPS e.max ZirCAD and Wieland ZENO Zr, and were loaded until fracture according to ISO 6872 (3-point bending test). An independent samples t test was used to assess significant differences of fracture strength (α=.05). Weibull statistical analysis of the flexural strength data provided 2 parameter estimates: Weibull modulus (m) and characteristic strength (σ(0)). The fractured surfaces of the specimens were evaluated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The investigation of the crystallographic state of the materials was performed with x-ray diffraction analysis (XRD) and Fourier transform infrared (FTIR) spectroscopy. Higher mean flexural strength (Plines zones). Both groups primarily sustained the tetragonal phase of zirconia and a negligible amount of the monoclinic phase. Although both zirconia ceramics presented similar fractographic and crystallographic properties, the higher flexural strength of WZ ceramics was associated with a lower m and more voids in their microstructure. These findings suggest a greater scattering of strength values and a flaw distribution that are expected to increase failure probability. Copyright © 2012 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  5. Comparison of shear test methods for evaluating the bond strength of resin cement to zirconia ceramic.

    Science.gov (United States)

    Kim, Jae-Hoon; Chae, Soyeon; Lee, Yunhee; Han, Geum-Jun; Cho, Byeong-Hoon

    2014-11-01

    This study compared the sensitivity of three shear test methods for measuring the shear bond strength (SBS) of resin cement to zirconia ceramic and evaluated the effects of surface treatment methods on the bonding. Polished zirconia ceramic (Cercon base, DeguDent) discs were randomly divided into four surface treatment groups: no treatment (C), airborne-particle abrasion (A), conditioning with Alloy primer (Kuraray Medical Co.) (P) and conditioning with Alloy primer after airborne-particle abrasion (AP). The bond strengths of the resin cement (Multilink N, Ivoclar Vivadent) to the zirconia specimens of each surface treatment group were determined by three SBS test methods: the conventional SBS test with direct filling of the mold (Ø 4 mm × 3 mm) with resin cement (Method 1), the conventional SBS test with cementation of composite cylinders (Ø 4 mm × 3 mm) using resin cement (Method 2) and the microshear bond strength (μSBS) test with cementation of composite cylinders (Ø 0.8 mm × 1 mm) using resin cement (Method 3). Both the test method and the surface treatment significantly influenced the SBS values. In Method 3, as the SBS values increased, the coefficients of variation decreased and the Weibull parameters increased. The AP groups showed the highest SBS in all of the test methods. Only in Method 3 did the P group show a higher SBS than the A group. The μSBS test was more sensitive to differentiating the effects of surface treatment methods than the conventional SBS tests. Primer conditioning was a stronger contributing factor for the resin bond to zirconia ceramic than was airborne-particle abrasion.

  6. Comparison of shear bond strength of two veneering ceramics to zirconia.

    Science.gov (United States)

    Rismanchian, Mansour; Shafiei, Soufia; Askari, Navid; Khodaeian, Niloufar

    2012-09-01

    Chip-off fracture of veneering porcelain has been described as the most frequent reason for the failure of zirconia-based fixed partial dentures. The purpose of this study was to evaluate the shear bond strength (SBS) of two commercial zirconia core ceramics to their corresponding veneering ceramics. Zirconia disks with 7-mm diameter and 3-mm height were prepared (Cercon and Biodenta systems) and veneered with recommended layering ceramics (Cercon ceram and 2 in 1 ceramic, respectively) (n = 10). The disks were polished with diamond paste and airborne-particle abraded before layering. The specimens were mounted in a T-shaped metal holder using autopolymerized acrylic resin and stored in 37°C distilled water for one week, after which they were subjected to thermal cycling. SBS of zirconia core to veneering ceramic was measured using a universal testing machine and failure modes were determined microscopically. Data were analyzed using t test (α < 0.05). Mean (±SD) SBS values were 27.19(±3.43) and 28.22(±4.08) MPa for Cercon and Biodenta systems, respectively, with no significant difference. Biodenta system showed more adhesive failure compared to more combined (adhesive and cohesive) failures in Cercon system. Within the limitations of this study it can be concluded that SBS of Biodenta and Cercon specimens were nearly the same, but the fracture mode of these two systems were different. Since Biodenta fracture pattern was predominantly adhesive, it seems that maybe Biodenta porcelain was stronger than Cercon porcelain where as its adhesive bond was weaker.

  7. Tribochemical Glass Ceramic Coating as a New Approach for Resin Adhesion to Zirconia.

    Science.gov (United States)

    Wandscher, Vinícius Felipe; Fraga, Sara; Pozzobon, João Luiz; Soares, Fabio Zovico Maxnuck; Foletto, Edson Luiz; May, Liliana Gressler; Valandro, Luiz Felipe

    To investigate the effects of a novel tribochemical silica coating technique with powders made from feldspathic ceramic and leucite-based ceramic on the bond strength of zirconia to resin cement before and after aging. Zirconia blocks were divided into 3 groups according to the material used for airborne-particle abrasion: 1) SP (control): silica-coated alumina particles; 2) FP: feldspathic ceramic powder; 3) LP: leucite glass-ceramic powder. After silanization, composite resin cylinders were cemented on the zirconia surface using a dual-curing resin cement. Prior to the shear bond strength (SBS) test, half of the samples (n = 15) were stored in distilled water for 24 h; the other half (n = 15) were submitted to aging (10,000 thermocycles of 5°C to 55°C; 150 days of water storage). The bond strength data were analyzed using two-way ANOVA and Tukey's test (α = 0.05). Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction analysis were performed. The initial bond strengths did not differ significantly between the groups (p = 0.053). However, after aging procedures, airborne-particle abrasion with feldspathic ceramic powder (FP) resulted in higher values of bond strength (p = 0.0001). SEM and EDS indicated that all the treatments promoted silica deposition on the Y-TZP surface ceramic. Airborne-particle abrasion with FP and LP induced a lower percentage of the monoclinic phase. Airborne abrasion with fine feldspathic ceramic particles is a novel tribochemical technique and appears to be suitable for improving the bond strength between zirconia and resin cements.

  8. High Speed Ultraviolet Phototransistors Based on an Ambipolar Fullerene Derivative

    KAUST Repository

    Huang, Wentao

    2018-03-13

    Combining high charge carrier mobility with ambipolar transport in light-absorbing organic semiconductors is highly desirable as it leads to enhanced charge photogeneration, and hence improved performance, in various optoelectronic devices including solar cells and photodetectors. Here we report the development of [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM)-based ultraviolet (UV) phototransistors with balanced electron and hole transport characteristics. The latter is achieved by fine-tuning the source–drain electrode work function using a self-assembled monolayer. Opto/electrical characterization of as-prepared ambipolar PC61BM phototransistors reveals promising photoresponse, particularly in the UV-A region (315–400 nm), with a maximum photosensitivity and responsivity of 9 × 103 and 3 × 103 A/W, respectively. Finally, the temporal response of the PC61BM phototransistors is found to be high despite the long channel length (10 s of μm) with typical switching times of <2 ms.

  9. Novel Viologen Derivative Based Uranyl Coordination Polymers Featuring Photochromic Behaviors.

    Science.gov (United States)

    Hu, Kong-Qiu; Wu, Qun-Yan; Mei, Lei; Zhang, Xiao-Lin; Ma, Lei; Song, Gang; Chen, Di-Yun; Wang, Yi-Tong; Chai, Zhi-Fang; Shi, Wei-Qun

    2017-12-19

    A series of novel uranyl coordination polymers have been synthesized by hydrothermal reactions. Both complexes 1 and 2 prosess two ipbp - ligands (H 2 ipbpCl=1-(3,5-dicarboxyphenyl)-4,4'-bipyridinium chloride), one uranyl cation, and two coordination water molecules, which can further extend to 2D networks through hydrogen bonding. In complex 1, two sets of equivalent nets are entangled together, resulting in a 2D + 2D → 3D polycatenated framework. In complex 2, the neighbouring equivalent nets interpenetrate each other, forming a twofold interpenetrated network. Complexes 3 and 4 are isomers, and both of them are constructed from (UO 2 ) 2 (OH) 2 dinuclear units, which are connected with four ipbp - ligands. The 3D structures of complexes 3 and 4 are similar along the b axis. Similar to other viologen-based coordination polymers, complexes 3 and 4 exhibit photochromic and thermochromic properties, which are rarely observed in actinide coordination polymers. Unlike the monotonous coordination mode in complexes 1-4, the ipbp - ligands feature a μ 3 -bridge through two kinds of coordination modes in complex 5. Notably, complex 5 presents a unique example in which terminal pyridine nitrogen atom is involved in the coordination. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. A new Co (III) complex of Schiff base derivative for electrochemical ...

    Indian Academy of Sciences (India)

    (III) complex of Schiff base derivative for electrochemical recognition of nitrite anion. HAKAN YILMAZ ABDULKADIR KOCAK MAOWULIDAN DILIMULATI YUNUS ZORLU MUBERRA ANDAC. REGULAR ARTICLE Volume 129 Issue 10 October ...

  11. Applications of yttria stabilized zirconia (YSZ) in catalysis

    NARCIS (Netherlands)

    Tsampas, M. N.; Sapountzi, F. M.; Vernoux, P.

    2015-01-01

    This article describes recent advances in the use of yttria stabilized zirconia (YSZ), an oxygen ion conductor, for catalytic applications. This ceramic material combines different functionalities such as good thermal stability, selective bulk oxygen mobility and high surface oxygen vacancy

  12. Light activated phase transformation of metastable tetragonal nanocrystalline zirconia

    DEFF Research Database (Denmark)

    Nielsen, Mette Skovgaard; Almdal, Kristoffer; van Lelieveld, A

    2012-01-01

    This study searches for small molecules, which can be generated by photoacid generators (PAGs) capable of inducing the tetragonal-to-monoclinic transformation in zirconia nanocrystals. Metastable tetragonal zirconia nanocrystals were exposed in alcohol suspension. X-ray diffraction analysis showed...... that water, HCl, HF, and NH3, all initiate phase transformation of tetragonal zirconia at room temperature, whereas NBu4Cl and NBu4OH do not. 2-(4-Methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine) was the most efficient (monoclinic volume fraction reached 0.57) out of the four tested PAGs....... For dispersion in a dimethacrylate matrix together with zirconia crystals, a monoclinic volume fraction of 0.19 was observed after 2 min of exposure to light, increasing to 0.6 after 30 min....

  13. Characterization of combustion synthesized zirconia powder by UV

    Indian Academy of Sciences (India)

    . The surface acidbase properties of these samples were also investigated by indicator titration method. The catalytic activity was probed with transfer hydrogenation reaction in liquid phase. It was found that combustion synthesized zirconia did ...

  14. Development of a novel zirconia dental post resistant to hydrothermal degradation

    Science.gov (United States)

    Camposilvan, E.; Marro, F. G.; Mestra, A.; Anglada, M. J.

    2012-02-01

    Tetragonal Zirconia Polycrystals stabilized with 3% mol. content of yttria (3Y-TZP) has excellent properties in terms of strength and fracture toughness. These properties are mostly imputable to the transformation toughening mechanism, by which the doped metastable tetragonal phase of zirconia transforms to monoclinic under applied stress ahead of a crack. This phenomenon is accompanied by a volume expansion of 5%, and increases the resistance to crack growth, thus leading to higher toughness and strength. An important drawback of this material is represented by the Low Temperature Degradation (LTD or aging), which consists in the progressive tetragonal-to-monoclinic phase transformation by the influence of water. This work focuses on the improvement of 3Y-TZP aging behavior in order to develop a novel dental post, by means of the addition of ceria from the surface. This was achieved through the impregnation of the pre-sintered samples with a solution containing Cerium, followed by sintering. Various pre-sintering temperatures were studied in terms of microstructure, mechanical properties and aging resistance. The novel zirconia dental posts developed in this work are much more resistant to LTD as compared to the base material with no loss in mechanical properties.

  15. Adaptation of zirconia crowns created by conventional versus optical impression: in vitro study.

    Science.gov (United States)

    Cetik, Sibel; Bahrami, Babak; Fossoyeux, InÈs; Atash, Ramin

    2017-06-01

    The aim of this study was to compare the precision of optical impression (Trios, 3Shape) versus that of conventional impression (Imprint IV, 3M-ESPE) with three different margins (shoulder, chamfer, and knife-edge) on Frasaco teeth. The sample comprised of 60 zirconia half-crowns, divided into six groups according to the type of impression and margin. Scanning electron microscopy enabled us to analyze the gap between the zirconia crowns and the Frasaco teeth, using ImageJ software, based on eight reproducible and standardized measuring points. No statistically significant difference was found between conventional impressions and optical impressions, except for two of the eight points. A statistically significant difference was observed between the three margin types; the chamfer and knife-edge finishing lines appeared to offer better adaptation results than the shoulder margin. Zirconia crowns created from optical impression and those created from conventional impression present similar adaptation. While offering identical results, the former have many advantages. In view of our findings, we believe the chamfer margin should be favored.

  16. Development of a novel zirconia dental post resistant to hydrothermal degradation

    International Nuclear Information System (INIS)

    Camposilvan, E; Marro, F G; Mestra, A; Anglada, M J

    2012-01-01

    Tetragonal Zirconia Polycrystals stabilized with 3% mol. content of yttria (3Y-TZP) has excellent properties in terms of strength and fracture toughness. These properties are mostly imputable to the transformation toughening mechanism, by which the doped metastable tetragonal phase of zirconia transforms to monoclinic under applied stress ahead of a crack. This phenomenon is accompanied by a volume expansion of 5%, and increases the resistance to crack growth, thus leading to higher toughness and strength. An important drawback of this material is represented by the Low Temperature Degradation (LTD or aging), which consists in the progressive tetragonal-to-monoclinic phase transformation by the influence of water. This work focuses on the improvement of 3Y-TZP aging behavior in order to develop a novel dental post, by means of the addition of ceria from the surface. This was achieved through the impregnation of the pre-sintered samples with a solution containing Cerium, followed by sintering. Various pre-sintering temperatures were studied in terms of microstructure, mechanical properties and aging resistance. The novel zirconia dental posts developed in this work are much more resistant to LTD as compared to the base material with no loss in mechanical properties.

  17. An in situ infrared study of dimethyl carbonate synthesis from carbon dioxide and methanol over zirconia

    International Nuclear Information System (INIS)

    Jung, Kyeong Taek; Bell, Alexis T.

    2001-01-01

    The mechanism of dimethyl carbonate (DMC) synthesis from methanol and carbon dioxide over monoclinic zirconia has been investigated using in situ infrared spectroscopy. The dissociative adsorption of methanol occurs more slowly than the adsorption of carbon dioxide, but the species formed from methanol are bound more strongly. Upon adsorption, the oxygen atom of methanol binds to coordinately unsaturated Zr4+ cations present at the catalyst surface. Rapid dissociation of the adsorbed methanol leads to the formation of a methoxide group (Zr-OCH3) and the release of a proton, which reacts with a surface hydroxyl group to produce water. Carbon dioxide inserts in the Zr-O bond of the methoxide to form a mondentate methyl carbonate group (Zr-OC(O)OCH3). This process is facilitated by the interactions of C and O atoms in CO2 with Lewis acid-base pairs of sites (Zr4+O2-) on the surface of the catalyst. Methyl carbonate species can also be produced via the reaction of methanol with carbon dioxide adsorbed in the form of bicarbonate species with methanol, a process that results in the transfer of a methyl group to the carbonate and restores a hydroxyl group to the zirconia surface. The decomposition of DMC on monoclinic zirconia has also been investigated and has been observed to occur via the reverse of the processes described for the synthesis of DMC

  18. Preparation, characterisation and activity of chromia-zirconia catalysts for propane dehydrogenation

    International Nuclear Information System (INIS)

    Cutrufello, M.G.; De Rossi, S.; Ferino, I.; Monaci, R.; Rombi, E.; Solinas, V.

    2005-01-01

    Dehydrogenation catalysts based on chromia supported on ZrO 2 , containing about 10 wt.% of chromium and increasing amounts of potassium (up to 4 wt.%), were prepared and characterised by chemical analysis, N 2 adsorption-desorption at 77 K, X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), temperature programmed reduction (TPR) and adsorption microcalorimetry of ammonia. Increasing K amounts deeply modify the ammonia adsorption behaviour, with a progressive decrease in the acidic features, which are completely lost when the K content attains 1 wt.%. Reduction of Cr species seems rather easy for chromia-zirconia and K-containing chromia-zirconia samples with K contents up to 0.5 wt.%. The onset of reduction shifts to higher temperatures as the K concentration increases. Catalytic testing was performed under atmospheric pressure at 813 K. Pure zirconia is very poorly active in propane dehydrogenation; also virtually inactive are the samples with a K content ≥1 wt.%. Conversion decreases as the K amount increases up to 0.5 wt.%, propene selectivity being close to 100 mol%. An induction period is observed for all the active samples, which attains a maximum in conversion before being deactivated by coking

  19. Fracture of Reduced-Diameter Zirconia Dental Implants Following Repeated Insertion.

    Science.gov (United States)

    Karl, Matthias; Scherg, Stefan; Grobecker-Karl, Tanja

    Achievement of high insertion torque values indicating good primary stability is a goal during dental implant placement. The objective of this study was to evaluate whether or not two-piece implants made from zirconia ceramic may be damaged as a result of torque application. A total of 10 two-piece zirconia implants were repeatedly inserted into polyurethane foam material with increasing density and decreasing osteotomy size. The insertion torque applied was measured, and implants were checked for fractures by applying the fluorescent penetrant method. Weibull probability of failure was calculated based on the recorded insertion torque values. Catastrophic failures could be seen in five of the implants from two different batches at insertion torques ranging from 46.0 to 70.5 Ncm, while the remaining implants (all belonging to one batch) survived. Weibull probability of failure seems to be low at the manufacturer-recommended maximum insertion torque of 35 Ncm. Chipping fractures at the thread tips as well as tool marks were the only otherwise observed irregularities. While high insertion torques may be desirable for immediate loading protocols, zirconia implants may fracture when manufacturer-recommended insertion torques are exceeded. Evaluating bone quality prior to implant insertion may be useful.

  20. Comparative Study of Shear Bond Strength of Three Veneering Ceramics to a Zirconia Core

    Directory of Open Access Journals (Sweden)

    Aalaei Sh

    2016-03-01

    Full Text Available Statement of Problem: Fracture of veneering porcelain has been described as the most frequent reason for the failure of zirconia-based fixed restorations. Objectives: The purpose of this study was to evaluate and compare the shear bond strength of a zirconium oxide core material to three commercial veneering ceramics. Materials and Methods: Three types of veneering ceramics were selected including IPS -emax Ceram, Vita VM9, and Cerabien. Thirty block specimens of zirconia core material were prepared in 4×4×9 mm dimensions. Three groups were created and the veneering ceramic was added to each of 10 blocks. Shear bond test was conducted with universal testing machine. Data were analyzed using one-way ANOVA (p = 0.05. Results: Mean shear bond strength values and standard deviations were 26.03 MPa (6.32, 23.85 MPa (4.01, and 19.16 MPa (3.72 for Vita VM9, IPS emax Ceram, and Cerabien, respectively. Cerabien ceramic showed more failure as compared to the other ceramics. However, there was no significant difference among the three veneering groups. Conclusions: Within the limitation of this study, it can be concluded that shear bond strength between zirconia core and three veneering ceramics was not significantly different.

  1. Synthesis and enhanced neuroprotective activity of C60-based ebselen derivatives

    International Nuclear Information System (INIS)

    Liu, X.-F.; Guan, W.-C.; Ke, W.-S.

    2007-01-01

    A C 60 -based ebselen derivative 4 was synthesized through the cycloaddition of C 60 with the azide (3) containing the ebselen component. It was obtained in a four-step synthesis starting from 2-(chloroseleno)benzoyl chloride and 2-(2-aminoethoxy)ethanol in 53% yield (based on consumed C 60 ). Its structure was characterized by 1 H NMR, 13 C NMR, IR, UV, and FAB-MS. To verify that the C 60 -based ebselen derivative 4 had enhanced antioxidative and neuroprotective activity, the C 60 derivative 5 and the ebselen derivative 6 were selected to treat cortical neuronal cells using the same procedures as with the C 60 -based ebselen derivative 4. The cellular viability of different derivative treatment groups was estimated by LDH leakage assay and MTT assay. At the same final concentration (30 μmol/L), the results showed that the antioxidative and protective potencies of the C 60 -based ebselen derivative 4 (MTT (OD) 0.340 ± 0.035, LDH release (UL -1 ) 4.80 ± 0.16) against H 2 O 2 -mediated neuronal injury have an advantage over those of C 60 derivative 5 (MTT (OD) 0.297 ± 0.036, LDH release (UL -1 ) 5.37 ± 0.31) and ebselen derivative 6 (MTT (OD) 0.267 ± 0.027, LDH release (UL -1 ) 5.85 ± 0.26). Correspondingly, the GPX activity of 4 (1.62 U/μmol) was higher than that of 5 (0.77 U/μmol) and 6 (1.24 U/μmol). These findings demonstrate that the incorporation of two components with similar biological activity (C 60 component and ebselen component) may be a desirable way of obtaining a new and more biologically effective C 60 -based compound. (author)

  2. Zirconia crowns - the new standard for single-visit dentistry?

    Science.gov (United States)

    Wiedhahn, Klaus; Fritzsche, Günter; Wiedhahn, Claudine; Schenk, Olaf

    2016-01-01

    Zirconia crowns combine the advantages of metal restorations, such as minimally invasive tooth preparation and ease of cementation, with those of full ceramic crowns, such as low thermal conductivity and tooth color. With the introduction of a high-speed sintering procedure, it is possible to produce and cement zirconia crowns and small monolithic bridges in a Cerec Single Visit procedure. This new procedure is compared to established chairside methods.

  3. Fracture resistance of monolithic zirconia molar crowns with reduced thickness

    OpenAIRE

    Nakamura, Keisuke; Harada, A.; Inagaki, R.; Kanno, Taro; Niwano, Y.; Milleding, Percy; Ørtengren, Ulf Thore

    2015-01-01

    This is the accepted manuscript version. Published version is available at Acta Odontologica Scandinavica Objectives. The purpose of the present study was to analyze the relationship between fracture load of monolithic zirconia crowns and axial/occlusal thickness, and to evaluate the fracture resistance of monolithic zirconia crowns with reduced thickness in comparison with that of monolithic lithium disilicate crowns with regular thickness. Materials and methods. Monolithic zi...

  4. Bonding effectiveness to different chemically pre-treated dental zirconia.

    Science.gov (United States)

    Inokoshi, Masanao; Poitevin, André; De Munck, Jan; Minakuchi, Shunsuke; Van Meerbeek, Bart

    2014-09-01

    The objective of this study was to evaluate the effect of different chemical pre-treatments on the bond durability to dental zirconia. Fully sintered IPS e.max ZirCAD (Ivoclar Vivadent) blocks were subjected to tribochemical silica sandblasting (CoJet, 3M ESPE). The zirconia samples were additionally pre-treated using one of four zirconia primers/adhesives (Clearfil Ceramic Primer, Kuraray Noritake; Monobond Plus, Ivoclar Vivadent; Scotchbond Universal, 3M ESPE; Z-PRIME Plus, Bisco). Finally, two identically pre-treated zirconia blocks were bonded together using composite cement (RelyX Ultimate, 3M ESPE). The specimens were trimmed at the interface to a cylindrical hourglass and stored in distilled water (7 days, 37 °C), after which they were randomly tested as is or subjected to mechanical ageing involving cyclic tensile stress (10 N, 10 Hz, 10,000 cycles). Subsequently, the micro-tensile bond strength was determined, and SEM fractographic analysis performed. Weibull analysis revealed the highest Weibull scale and shape parameters for the 'Clearfil Ceramic Primer/mechanical ageing' combination. Chemical pre-treatment of CoJet (3M ESPE) sandblasted zirconia using Clearfil Ceramic Primer (Kuraray Noritake) and Monobond Plus (Ivoclar Vivadent) revealed a significantly higher bond strength than when Scotchbond Universal (3M ESPE) and Z-PRIME Plus (Bisco) were used. After ageing, Clearfil Ceramic Primer (Kuraray Noritake) revealed the most stable bond durability. Combined mechanical/chemical pre-treatment, the latter with either Clearfil Ceramic Primer (Kuraray Noritake) or Monobond Plus (Ivoclar Vivadent), resulted in the most durable bond to zirconia. As a standard procedure to durably bond zirconia to tooth tissue, the application of a combined 10-methacryloyloxydecyl dihydrogen phosphate/silane ceramic primer to zirconia is clinically highly recommended.

  5. Synthesis of zirconia colloidal dispersions by forced hydrolysis

    Directory of Open Access Journals (Sweden)

    JELENA P. MARKOVIC

    2006-06-01

    Full Text Available Different zirconia colloidal dispersions (sols were prepared from zirconyl oxynitrate and zirconyl oxychloride solutions by forced hydrolysis. Vigorously stirred acidic solutions of these salts were refluxed at 102 oC for 24 h. Characterization of the obtained sols (pH, solid phase content, crystal structure was performed by potentiometric, XRD, TGA/DTA and SEM measurements. The prepared sols contained almost spherical monoclinic hydrated zirconia particles 7–10 nm in diameter.

  6. A systematic review of the clinical survival of zirconia implants.

    Science.gov (United States)

    Hashim, Dena; Cionca, Norbert; Courvoisier, Delphine S; Mombelli, Andrea

    2016-09-01

    The aim of this review was to evaluate the clinical success and survival rates of zirconia ceramic implants after at least 1 year of function and to assess if there is sufficient evidence to justify using them as alternatives to titanium implants. An electronic search in MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Clinical Trials (CENTRAL) databases was performed in April 2015 by two independent examiners to retrieve clinical studies focusing on the survival rate of zirconia implants after at least 1 year of function. Implant survival was estimated using the overall proportion reported in the studies with a Clopper-Pearson 95 % confidence interval (random effect model with a Der-Simonian Laird estimate). Fourteen articles were selected out of the 1519 titles initially screened. The overall survival rate of zirconia one- and two-piece implants was calculated at 92 % (95 % CI 87-95) after 1 year of function. The survival of implants at 1 year for the selected studies revealed considerable heterogeneity. In spite of the unavailability of sufficient long-term evidence to justify using zirconia oral implants, zirconia ceramics could potentially be the alternative to titanium for a non-metallic implant solution. However, further clinical studies are required to establish long-term results, and to determine the risk of technical and biological complications. Additional randomized controlled clinical trials examining two-piece zirconia implant systems are also required to assess their survival and success rates in comparison with titanium as well as one-piece zirconia implants. Zirconia implants provide a potential alternative to titanium ones. However, clinicians must be aware of the lack of knowledge regarding long-term outcomes and specific reasons for failure.

  7. Chemical interaction mechanism of 10-MDP with zirconia.

    Science.gov (United States)

    Nagaoka, Noriyuki; Yoshihara, Kumiko; Feitosa, Victor Pinheiro; Tamada, Yoshiyuki; Irie, Masao; Yoshida, Yasuhiro; Van Meerbeek, Bart; Hayakawa, Satoshi

    2017-03-30

    Currently, the functional monomer 10-methacryloyloxy-decyl-dihydrogen-phosphate (10-MDP) was documented to chemically bond to zirconia ceramics. However, little research has been conducted to unravel the underlying mechanisms. This study aimed to assess the chemical interaction and to demonstrate the mechanisms of coordination between 10-MDP and zirconium oxide using 1 H and 31 P magic angle spinning (MAS) nuclear magnetic resonance (NMR) and two dimensional (2D) 1 H →  31 P heteronuclear correlation (HETCOR) NMR. In addition, shear bond-strength (SBS) tests were conducted to determine the effect of 10-MDP concentration on the bonding effectiveness to zirconia. These SBS tests revealed a 10-MDP concentration-dependent SBS with a minimum of 1-ppb 10-MDP needed. 31 P-NMR revealed that one P-OH non-deprotonated of the PO 3 H 2 group from 10-MDP chemically bonded strongly to zirconia. 1 H- 31 P HETCOR NMR indicated that the 10-MDP monomer can be adsorbed onto the zirconia particles by hydrogen bonding between the P=O and Zr-OH groups or via ionic interactions between partially positive Zr and deprotonated 10-MDP (P-O - ). The combination of 1 H NMR and 2D 1 H- 31 P HETCOR NMR enabled to describe the different chemical states of the 10-MDP bonds with zirconia; they not only revealed ionic but also hydrogen bonding between 10-MDP and zirconia.

  8. Guided tooth preparation for a pediatric zirconia crown.

    Science.gov (United States)

    Lee, Ju-Hyoung

    2018-03-01

    Unesthetic primary incisors can produce negative self-perceptions in preschool-aged children. In recent years, because of increased esthetic demands, prefabricated zirconia crowns have become increasingly popular. However, zirconia crowns cannot be crimped, and the clinician must prepare the teeth to fit the zirconia crowns. Therefore, extended preparation and fitting times are necessary, especially for inexperienced practitioners. A 1- to 2-millimeter subgingival feather margin also is required. Gingival hemorrhage after subgingival preparation compromises the retention of zirconia crowns. In this clinical report, the author presents a step-by-step description of the clinical and laboratory procedures for restoring a discolored traumatized incisor with a zirconia crown. The author used a polyvinyl siloxane occlusal registration material as an impression material and made 2 identical casts. The author fabricated 3 reduction guides after prospective tooth preparation on the casts. The author rapidly prepared the discolored incisor with the reduction guides and ultrasonic burs. A zirconia crown provided an optimal esthetic result and gingival health. Because the reduction guides provided a visibility intraorally, fast tooth reduction, less trial placement, and passive adaptation of the crown were successful. Because the ultrasonic burs prevented gingival injuries, hemorrhage control was not necessary. The presented technique reduced the patient's discomfort and total chair time. Therefore, this alternative technique is helpful for inexperienced practitioners. Copyright © 2018 American Dental Association. Published by Elsevier Inc. All rights reserved.

  9. Synthesis and catalytic activity of polysaccharide templated nanocrystalline sulfated zirconia

    Science.gov (United States)

    Sherly, K. B.; Rakesh, K.

    2014-01-01

    Nanoscaled materials are of great interest due to their unique enhanced optical, electrical and magnetic properties. Sulfate-promoted zirconia has been shown to exhibit super acidic behavior and high activity for acid catalyzed reactions. Nanocrystalline zirconia was prepared in the presence of polysaccharide template by interaction between ZrOCl2ṡ8H2O and chitosan template. The interaction was carried out in aqueous phase, followed by the removal of templates by calcination at optimum temperature and sulfation. The structural and textural features were characterized by powder XRD, TG, SEM and TEM. XRD patterns showed the peaks of the diffractogram were in agreement with the theoretical data of zirconia with the catalytically active tetragonal phase and average crystalline size of the particles was found to be 9 nm, which was confirmed by TEM. TPD using ammonia as probe, FTIR and BET surface area analysis were used for analyzing surface features like acidity and porosity. The BET surface area analysis showed the sample had moderately high surface area. FTIR was used to find the type species attached to the surface of zirconia. UV-DRS found the band gap of the zirconia was found to be 2.8 eV. The benzylation of o-xylene was carried out batchwise in atmospheric pressure and 433K temperature using sulfated zirconia as catalyst.

  10. Chemical interaction mechanism of 10-MDP with zirconia

    Science.gov (United States)

    Nagaoka, Noriyuki; Yoshihara, Kumiko; Feitosa, Victor Pinheiro; Tamada, Yoshiyuki; Irie, Masao; Yoshida, Yasuhiro; van Meerbeek, Bart; Hayakawa, Satoshi

    2017-03-01

    Currently, the functional monomer 10-methacryloyloxy-decyl-dihydrogen-phosphate (10-MDP) was documented to chemically bond to zirconia ceramics. However, little research has been conducted to unravel the underlying mechanisms. This study aimed to assess the chemical interaction and to demonstrate the mechanisms of coordination between 10-MDP and zirconium oxide using 1H and 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) and two dimensional (2D) 1H → 31P heteronuclear correlation (HETCOR) NMR. In addition, shear bond-strength (SBS) tests were conducted to determine the effect of 10-MDP concentration on the bonding effectiveness to zirconia. These SBS tests revealed a 10-MDP concentration-dependent SBS with a minimum of 1-ppb 10-MDP needed. 31P-NMR revealed that one P-OH non-deprotonated of the PO3H2 group from 10-MDP chemically bonded strongly to zirconia. 1H-31P HETCOR NMR indicated that the 10-MDP monomer can be adsorbed onto the zirconia particles by hydrogen bonding between the P=O and Zr-OH groups or via ionic interactions between partially positive Zr and deprotonated 10-MDP (P-O-). The combination of 1H NMR and 2D 1H-31P HETCOR NMR enabled to describe the different chemical states of the 10-MDP bonds with zirconia; they not only revealed ionic but also hydrogen bonding between 10-MDP and zirconia.

  11. Sliding Contact Fatigue of Graded Zirconia with External Esthetic Glass

    Science.gov (United States)

    Ren, L.; Janal, M.N.; Zhang, Y.

    2011-01-01

    Veneer chipping and fracture are common failure modes for porcelain-veneered zirconia dental restorations. We hypothesized that the graded glass/zirconia/glass with external esthetic glass (e-GZG) can increase the lifetime and improve resistance to veneer chipping and fracture relative to porcelain-veneered zirconia, while providing necessary esthetics. Previously, we have demonstrated that a graded glass-zirconia surface possesses excellent resistance to occlusal-like sliding contact fatigue. Here, we investigated the sliding contact fatigue response of this graded glass-zirconia surface with external esthetic glass. This external glass is essential for shade options, for preventing excessive wear of opposing dentition, and for protecting Y-TZP from hydrothermal degradation. e-GZG plates were bonded to composite blocks and subjected to prolonged sliding contact up to 10 million cycles at 200 N in water. The resistance to sliding contact fatigue of e-GZG matches that of monolithic Y-TZP, and both of these materials demonstrated lifetimes that were orders of magnitude longer than that of porcelain-veneered zirconia. Graded e-GZG is a promising restorative material. PMID:21666105

  12. Synthesis and catalytic activity of polysaccharide templated nanocrystalline sulfated zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Sherly, K. B.; Rakesh, K. [Mahatma Gandhi University Regional Research Center in Chemistry, Department of Chemistry, Mar Athanasius College, Kothamangalam-686666, Kerala (India)

    2014-01-28

    Nanoscaled materials are of great interest due to their unique enhanced optical, electrical and magnetic properties. Sulfate-promoted zirconia has been shown to exhibit super acidic behavior and high activity for acid catalyzed reactions. Nanocrystalline zirconia was prepared in the presence of polysaccharide template by interaction between ZrOCl{sub 2}⋅8H{sub 2}O and chitosan template. The interaction was carried out in aqueous phase, followed by the removal of templates by calcination at optimum temperature and sulfation. The structural and textural features were characterized by powder XRD, TG, SEM and TEM. XRD patterns showed the peaks of the diffractogram were in agreement with the theoretical data of zirconia with the catalytically active tetragonal phase and average crystalline size of the particles was found to be 9 nm, which was confirmed by TEM. TPD using ammonia as probe, FTIR and BET surface area analysis were used for analyzing surface features like acidity and porosity. The BET surface area analysis showed the sample had moderately high surface area. FTIR was used to find the type species attached to the surface of zirconia. UV-DRS found the band gap of the zirconia was found to be 2.8 eV. The benzylation of o-xylene was carried out batchwise in atmospheric pressure and 433K temperature using sulfated zirconia as catalyst.

  13. Condensation of tetragonal zirconia polycrystals by reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, I-M. [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Yeh, S.-W. [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Chiou, S.-Y. [Department of Mold and Die Engineering, National Kaohsiung University of Applied Science, Kaohsiung, Taiwan (China); Gan Dershin [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China)]. E-mail: dgan@mail.nsysu.edu.tw; Shen Pouyan [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

    2005-11-22

    Reactive sputtering on metallic Zr target under various oxygen flow rates was employed to produce nanocrystalline zirconia condensates, which were collected on a carbon-coated collodion film for analytical electron microscopic observations. With an Ar flow rate of 28 sccm, the collected condensates are cubic and tetragonal (t-) zirconia less than 10 nm in size under 0-2 sccm oxygen flow rate and increased to 10-20 nm in size with partial t- to monoclinic (m-) zirconia transformation at 3 sccm. Between 4 and 4.5 sccm, t-zirconia polycrystals (TZP) about 20 nm in grain size were formed by coalescence of the t-zirconia condensates. Above 6 sccm, the (111) and {l_brace}100{r_brace} specific coalescence as well as random attachment prevailed to form larger (> 30 nm) individual condensates of m-zirconia as the critical size of martensitic t-m transformation is exceeded. The TZP formation can be accounted for by the small grain size, the presence of low-valence Zr cation and the lateral constraint of neighboring grains.

  14. Properties of zirconia after plasma treatment

    Science.gov (United States)

    Alekseenko, V. P.; Kulkov, S. N.

    2017-09-01

    The influence of high-frequency plasma treatment on the properties of zirconia powder is shown in the work. The powder was produced by a plasma-chemical method. The powders had a foamy form with the size of agglomerates of 5-10 μm and crystallites of 20-50 nm. The powders were treated by the pulse plasma unit with dielectric barrier discharge generator. It was shown that the plasma processing changes the acidity of water-powder suspensions from 8.1 to 4.3 pH, which signifies the powders' wettability improvement. It was revealed that more intensive mixing using ultrasound influences the acidity level, reducing it in comparison with mixing by paddle-type agitator. It was shown that these changes of surface properties have relaxation by 4% per day and extrapolation of this dependence shows that the powder will have initial properties after 400 hours storage at room conditions.

  15. Light transmittance of zirconia as a function of thickness and microhardness of resin cements under different thicknesses of zirconia

    Science.gov (United States)

    Egilmez, Ferhan; Ergun, Gulfem; Kaya, Bekir M.

    2013-01-01

    Objective: The objective of this study was to compare microhardness of resin cements under different thicknesses of zirconia and the light transmittance of zirconia as a function of thickness. Study design: A total of 126 disc-shaped specimens (2 mm in height and 5 mm in diameter) were prepared from dual-cured resin cements (RelyX Unicem, Panavia F and Clearfil SA cement). Photoactivation was performed by using quartz tungsten halogen and light emitting diode light curing units under different thicknesses of zirconia. Then the specimens (n=7/per group) were stored in dry conditions in total dark at 37°C for 24 h. The Vicker’s hardness test was performed on the resin cement layer with a microhardness tester. Statistical significance was determined using multifactorial analysis of variance (ANOVA) (alpha=.05). Light transmittance of different thicknesses of zirconia (0.3, 0.5 and 0.8 mm) was measured using a hand-held radiometer (Demetron, Kerr). Data were analyzed using one-way ANOVA test (alpha=.05). Results: ANOVA revealed that resin cement and light curing unit had significant effects on microhardness (p zirconia thickness resulted in lower transmittance. There was no correlation between the amount of light transmitted and microhardness of dual-cured resin cements (r = 0.073, p = 0.295). Conclusion: Although different zirconia thicknesses might result in insufficient light transmission, dual-cured resin cements under zirconia restorations could have adequate microhardness. Key words:Zirconia, microhardness, light transmittance, resin cement. PMID:23385497

  16. Antagonist wear by polished zirconia crowns.

    Science.gov (United States)

    Hartkamp, Oliver; Lohbauer, Ulrich; Reich, Sven

    The aim of this in vivo study was to measure antagonist wear caused by polished monolithic posterior zirconia crowns over a 24-month period using the intraoral digital impression (IDI) technique. Thirteen zirconia crowns were placed in nine patients. The crowns and adjacent teeth were captured using an intraoral scanner (Lava C.O.S.). The corresponding antagonist teeth and the respective neighboring teeth were also scanned. Scanning was performed immediately after the restoration (baseline) as well as 12 and 24 months after crown placement. Geomagic Qualify software was used to superimpose the follow-up data sets onto the corresponding baseline data set, identify wear sites, and measure maximum vertical height loss in each individual wear site. Overall antagonist wear was then determined as the mean of wear rates measured in all of the individual antagonist units. In addition, wear rates in enamel and ceramic antagonists were analyzed as part of the scope of this study. The maximum mean wear with standard deviation (SD) in the overall sample with a total of nine patients, 13 antagonist units, and 98 evaluable wear sites was 86 ± 23 µm at 12 months, and 103 ± 39 µm at 24 months. The maximum mean wear in the enamel antagonist subgroup was 87 ± 41 µm at 12 months, and 115 ± 71 µm at 24 months; and in the ceramic antagonist subgroup 107 ± 22 µm at 12 months, and 120 ± 27 µm at 24 months. The wear rates determined in this study are comparable to those of existing studies. The IDI technique of wear analysis can be carried out in a practical manner and produces useful results.

  17. Biological reactivity of zirconia-hydroxyapatite composites.

    Science.gov (United States)

    Silva, Viviane V; Lameiras, Fernando S; Lobato, Zélia I P

    2002-01-01

    Materials and devices intended for end-use applications as implants and medical devices must be evaluated to determine their biocompatibility potential in contact with physiological systems. The use of standard practices of biological testing provides a reasonable level of confidence concerning the response of a living organism to a given material or device, as well as guidance in selecting the proper procedures to be carried out for the screening of new or modified materials. This article presents results from cytotoxicity assays of cell culture, skin irritation, and acute toxicity by systemic and intracutaneous injections for powders, ceramic bodies, and extract liquids of hydroxyapatite (HA), calcia partially stabilized zirconia (ZO), and two types of zirconia-hydroxyapatite composites (Z4H6 and Z6H4) with potential for future use as orthopedic and dental implants. They indicate that these materials present potential for this type of application because they meet the requirements of the standard practices recommended for evaluating the biological reactivity of ATCC cell cultures (CCL1 NCTC clone 929 of mouse connective tissue and CCL 81 of monkey connective tissue) and animals (rabbit and mouse) with direct or indirect patient contact, or by the injection of specific extracts prepared from the material under test. In addition, studies involving short-term intramuscular and long-term implantation assays to estimate the reaction of living tissue to the composites studied, and investigations on long-term effects that these materials can cause on the cellular metabolism, are already in progress. Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 583-590, 2002

  18. I. Diamino telechelic polybutadienes: Synthesis, characterization and melt coupling. II. Poly(epsilon-caprolactone-beta-poly(ethylene glycol) polymeric nanoparticles for drug delivery. III. Zirconia based cellulosic HPLC chiral stationary phase for enantioseparations

    Science.gov (United States)

    Ji, Shengxiang

    surfaces was measured and ˜51-67% conjugation was obtained. Chemical modification of celluloses leads to the production of high value-added materials. Phosphonic acid, carboxylic acid, and methacrylate functionalized carbamate celluloses were synthesized through direct alkylation of carbamate celluloses. These functionalized carbamate celluloses were then deposited on zirconia particles, which were used as chiral stationary phases for HPLC. The separation and retention factors of columns packed by cellulose coated zirconia were evaluated on thirteen pairs of racemates. The results were also compared with the results of a commercial cellulosic silica column under same test conditions.

  19. Methacrylate bonding to zirconia by in situ silica nanoparticle surface deposition.

    Science.gov (United States)

    Oliveira-Ogliari, Aline; Collares, Fabrício M; Feitosa, Victor P; Sauro, Salvatore; Ogliari, Fabrício A; Moraes, Rafael R

    2015-01-01

    This study introduces an innovative method to enhance adhesion of methacrylate-based cements to yttria-stabilized zirconia (Y-TZP) by means of a silica-nanoparticle deposition process. Two alkoxide organic precursors, tetraethyl-orthosilicate (TEOS) and zirconium tert-butoxide (ZTB) were diluted in hexane at different concentrations in order to obtain several experimental materials to enhance deposition of a SiO(x) reactive layer to Y-TZP. This deposition was attained via sintering alkoxide precursors directly on pre-sintered zirconia (infiltration method—INF) or application on the surface of fully sintered zirconia (coating method—COA). Untreated specimens and a commercial tribochemical silica coating were also tested as controls and all the treated Y-TZP specimens were analyzed using SEM-EDX. Specimens were bonded using silane, adhesive and dual-cure luting cement and submitted to shear bond strength test after different water storage periods (24 h, 3-, 6- and 12-months). SEM-EDX revealed Y-TZP surface covered by silica nanoclusters. The morphology of silica-covered Y-TZP surfaces was influenced by sintering method, employed to deposit nanoclusters. High bond strength (MPa) was observed when using COA method; highest TEOS percentage achieved the greatest bond strengths to Y-TZP surface (36.7±6.3 at 24 h). However, bonds stability was dependent on ZTB presence (32.9±9.7 at 3 months; 32.3±7.1 at 6 months). Regarding INF method, the highest and more stable resin-zirconia bond strength was attained when using experimental solutions containing TEOS and no ZTB. Both sintering methods tested in this study were able to achieve a bonding performance similar to that of classic tribochemical strategies. This study demonstrates that it is possible to achieve a reliable and long-lasting bonding between yttria-stabilized zirconia ceramic and methacrylate-based cements when using this novel, simple, and cost-effective bonding approach. Copyright © 2014 Academy of Dental

  20. Load at fracture of monolithic and bilayered zirconia crowns with and without a cervical zirconia collar.

    Science.gov (United States)

    Øilo, Marit; Kvam, Ketil; Gjerdet, Nils Roar

    2016-05-01

    The effect of anatomic contour design in all or parts of zirconia crowns is uncertain regarding clinical reliability and survival rates. The purpose of this in vitro study was to compare the load at fracture of monolithic, anatomic contour zirconia crowns with bilayered crowns with and without a cervical zirconia collar. Thirty zirconia crowns were fabricated for a shallow chamfer molar preparation, 10 with a normal core-veneer design, 10 with a core-veneer design with an additional cervical collar of zirconia, and 10 with a monolithic, anatomic contour design. Veneering ceramic was applied to the first 20 specimens to create an anatomic form. All crowns were cemented to epoxy abutments and loaded until complete fracture with a clinically relevant test method. The fracture modes and load at fracture were recorded. Statistically significant differences were found in the load at fracture and fracture modes among the test groups (Pcrown margin, mostly in the proximal region. The mean load at fracture was 4091 N for the normal core-veneer design, 4712 N for the collar design, and 6517 N for the monolithic, anatomic contour design. Monolithic, anatomical contour design gave higher loads at fracture than traditional core-veneer design. Crowns with a cervical zirconia collar had higher load at fracture than the core-veneer design, but lower than the monolithic crowns. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  1. Marginal accuracy of computer-aided design- and computer-aided manufacturing-fabricated full-arch zirconia restoration

    Directory of Open Access Journals (Sweden)

    Juntavee N

    2018-02-01

    Full Text Available Niwut Juntavee,1 Issarawas Sirisathit2 1Department of Prosthodontics, 2Division of Biomaterials and Prosthodontics Research, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand Objective: This study evaluated marginal accuracy of full-arch zirconia restoration fabricated from two digital computer-aided design and computer-aided manufacturing (CAD-CAM systems (Trios-3 and CS3500 in comparison to conventional cast metal restoration. Materials and methods: A stainless steel model comprising two canine and two molar abutments was used as a master model for full-arch reconstruction. The canine and molar abutments were machined in a cylindrical shape with 5° taper and chamfer margin. The CAD-CAM systems based on the digital approach were used to construct the full-arch zirconia restoration. The conventional cast metal restoration was fabricated according to a conventional lost-wax technique using nickel–chromium alloys. Ten restorations were fabricated from each system. The marginal accuracy of each restoration was determined at four locations for each abutment. An analysis of variance (ANOVA and Tukey’s honest significant difference (HSD multiple comparisons were used to determine statistically significant difference at 95% confidence interval. Results: The mean values of marginal accuracy of restorations fabricated from conventional casting, Trios-3, and CS3500 were 48.59±4.16 μm, 53.50±5.66 μm, and 56.47±5.52 μm, respectively. ANOVA indicated significant difference in marginal fit of restorations among various systems. The marginal discrepancy of zirconia restoration fabricated from the CS3500 system demonstrated significantly larger gap than that fabricated from the 3Shape system (p<0.05. Tukey’s HSD multiple comparisons indicated that the zirconia restoration fabricated from either CS3500 or Trios-3 demonstrated a significantly larger marginal gap than the conventional cast metal restoration (p<0.05. Conclusion: Full

  2. Masking ability of a zirconia ceramic on composite resin substrate shades

    Directory of Open Access Journals (Sweden)

    Farhad Tabatabaian

    2017-01-01

    Conclusion: Within the limitations of this study, it can be concluded that the tested zirconia ceramic could not thoroughly mask different shades of the composite resin substrates. Moreover, color masking of zirconia depends on the shade of substrate.

  3. Application of Monolithic Zirconia Ceramics in Dental Practice: A Case History Report.

    Science.gov (United States)

    Kim, Hee-Kyung; Kim, Sung-Hun; Lee, Jai-Bong; Han, Jung-Suk; Yeo, In-Sung

    2016-01-01

    Monolithic zirconia restorations increasingly have been used in dental practice in recent years and demonstrate superior mechanical performance compared with porcelain-veneered zirconia restorations. Recent advances in manufacturing technology have made possible the fabrication of translucent monolithic zirconia ceramics. This case report describes three clinical examples of monolithic zirconia fixed dental prostheses being used in the anterior and posterior regions and exhibiting acceptable esthetic results.

  4. Bioactive and Thermally Compatible Glass Coating on Zirconia Dental Implants

    Science.gov (United States)

    Kirsten, A.; Hausmann, A.; Weber, M.; Fischer, J.

    2015-01-01

    The healing time of zirconia implants may be reduced by the use of bioactive glass coatings. Unfortunately, existing glasses are either bioactive like Bioglass 45S5 but thermally incompatible with the zirconia substrate, or they are thermally compatible but exhibit only a very low level of bioactivity. In this study, we hypothesized that a tailored substitution of alkaline earth metals and alkaline metals in 45S5 can lead to a glass composition that is both bioactive and thermally compatible with zirconia implants. A novel glass composition was analyzed using x-ray fluorescence spectroscopy, dilatometry, differential scanning calorimetry, and heating microscopy to investigate its chemical, physical, and thermal properties. Bioactivity was tested in vitro using simulated body fluid (SBF). Smooth and microstructured glass coatings were applied using a tailored spray technique with subsequent thermal treatment. Coating adhesion was tested on implants that were inserted in bovine ribs. The cytocompatibility of the coating was analyzed using L929 mouse fibroblasts. The coefficient of thermal expansion of the novel glass was shown to be slightly lower (11.58·10–6 K–1) than that of the zirconia (11.67·10–6 K–1). After storage in SBF, the glass showed reaction layers almost identical to the bioactive glass gold standard, 45S5. A process window between 800 °C and 910 °C was found to result in densely sintered and amorphous coatings. Microstructured glass coatings on zirconia implants survived a minimum insertion torque of 60 Ncm in the in vitro experiment on bovine ribs. Proliferation and cytotoxicity of the glass coatings was comparable with the controls. The novel glass composition showed a strong adhesion to the zirconia substrate and a significant bioactive behavior in the SBF in vitro experiments. Therefore, it holds great potential to significantly reduce the healing time of zirconia dental implants. PMID:25421839

  5. Bioactive and thermally compatible glass coating on zirconia dental implants.

    Science.gov (United States)

    Kirsten, A; Hausmann, A; Weber, M; Fischer, J; Fischer, H

    2015-02-01

    The healing time of zirconia implants may be reduced by the use of bioactive glass coatings. Unfortunately, existing glasses are either bioactive like Bioglass 45S5 but thermally incompatible with the zirconia substrate, or they are thermally compatible but exhibit only a very low level of bioactivity. In this study, we hypothesized that a tailored substitution of alkaline earth metals and alkaline metals in 45S5 can lead to a glass composition that is both bioactive and thermally compatible with zirconia implants. A novel glass composition was analyzed using x-ray fluorescence spectroscopy, dilatometry, differential scanning calorimetry, and heating microscopy to investigate its chemical, physical, and thermal properties. Bioactivity was tested in vitro using simulated body fluid (SBF). Smooth and microstructured glass coatings were applied using a tailored spray technique with subsequent thermal treatment. Coating adhesion was tested on implants that were inserted in bovine ribs. The cytocompatibility of the coating was analyzed using L929 mouse fibroblasts. The coefficient of thermal expansion of the novel glass was shown to be slightly lower (11.58 · 10(-6) K(-1)) than that of the zirconia (11.67 · 10(-6) K(-1)). After storage in SBF, the glass showed reaction layers almost identical to the bioactive glass gold standard, 45S5. A process window between 800 °C and 910 °C was found to result in densely sintered and amorphous coatings. Microstructured glass coatings on zirconia implants survived a minimum insertion torque of 60 Ncm in the in vitro experiment on bovine ribs. Proliferation and cytotoxicity of the glass coatings was comparable with the controls. The novel glass composition showed a strong adhesion to the zirconia substrate and a significant bioactive behavior in the SBF in vitro experiments. Therefore, it holds great potential to significantly reduce the healing time of zirconia dental implants. © International & American Associations for Dental

  6. Residual Stresses in Porcelain-veneered Zirconia Prostheses

    Science.gov (United States)

    Baldassarri, Marta; Stappert, Christian F. J.; Wolff, Mark S.; Thompson, Van P.; Zhang, Yu

    2012-01-01

    Objectives Compressive stress has been intentionally introduced into the overlay porcelain of zirconia-ceramic prostheses to prevent veneer fracture. However, recent theoretical analysis has predicted that the residual stresses in the porcelain may be also tensile in nature. This study aims to determine the type and magnitude of the residual stresses in the porcelain veneers of full-contour fixed-dental prostheses (FDPs) with an anatomic zirconia coping design and in control porcelain with the zirconia removed using a well-established Vickers indentation method. Methods Six 3-unit zirconia FDPs were manufactured (NobelBiocare, Gothenburg, Sweden). Porcelain was hand-veneered using a slow cooling rate. Each FDP was sectioned parallel to the occlusal plane for Vickers indentations (n = 143; load = 9.8 N; dwell time = 5 s). Tests were performed in the veneer of porcelain-zirconia specimens (bilayers, n = 4) and porcelain specimens without zirconia cores (monolayers, n = 2). Results The average crack lengths and standard deviation, in the transverse and radial directions (i.e. parallel and perpendicular to the veneer/core interface, respectively), were 67 ± 12 μm and 52 ± 8 μm for the bilayers and 64 ± 8 μm and 64 ± 7 μm for the monolayers. These results indicated a major hoop compressive stress (~40 to 50 MPa) and a moderate radial tensile stress (~10 MPa) in the bulk of the porcelain veneer. Significance Vickers indentation is a powerful method to determine the residual stresses in veneered zirconia systems. Our findings revealed the presence of a radial tensile stress in the overlay porcelain, which may contributed to the large clinical chip fractures observed in these prostheses. PMID:22578663

  7. Orthodontic bracket bonding to glazed full-contour zirconia

    Directory of Open Access Journals (Sweden)

    Ji-Young Kwak

    2016-05-01

    Full Text Available Objectives This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces. Materials and Methods Glazed zirconia (except for the control, Zirkonzahn Prettau disc surfaces were pre-treated: PO (control, polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometry, scanning electron microscopy, and electron dispersive spectroscopy. A zirconia primer (Z-Prime Plus, Z or a silane primer (Monobond-S, S was then applied to the surfaces, yielding 7 groups (PO-Z, BR-Z, PP-S, HF-S, AA-S, AA-Z, and CJ-S. Metal bracket-bonded specimens were stored in water for 24 hr at 37℃, and thermocycled for 1,000 cycles. Their bond strengths were measured using the wire loop method (n = 10. Results Except for BR, the surface pre-treatments failed to expose the zirconia substructure. A significant difference in bond strengths was found between AA-Z (4.60 ± 1.08 MPa and all other groups (13.38 ± 2.57 - 15.78 ± 2.39 MPa, p < 0.05. For AA-Z, most of the adhesive remained on the bracket. Conclusions For bracket bonding to glazed zirconia, a simple application of silane to the cleaned surface is recommended. A zirconia primer should be used only when the zirconia substructure is definitely exposed.

  8. Study of polar and nonpolar substituted benzenes and aromatic isomers on carbon-coated zirconia and alkyl bonded phases.

    Science.gov (United States)

    Jackson, Paul T; Carr, Peter W

    2002-06-07

    Retention factors of polar and non-polar mono- and di-substituted benzene derivatives were measured on carbon coated zirconia (C/ZrO2) and an alkyl modified silica using water-acetonitrile mobile phases. Published data on porous graphitic carbon phases (PGC) were used to facilitate comparisons between the two types of carbon media. This work showed that retention on both C/ZrO2 and PGC is much more sensitive to the solute polarizability, dipolarity, and shape than on aliphatic phases. For simple disubstituted benzenes there was no general clear cut advantage in terms of chromatographic selectivity to using a carbon-based phase over a bonded phase silica; however, the selectivities towards such isomers are quite different on the two types of media. In contradistinction to their effect on alkyl bonded phase retention, addition of a dipolar substituent and weak hydrogen bond acceptor to a benzene ring almost always increases the solute's retention on C/ZrO2 and PGC.

  9. Combined novel bonding method of resin to zirconia ceramic in dentistry: a pilot study

    NARCIS (Netherlands)

    Aboushelib, M.N.; Matinlinna, J.P.

    2011-01-01

    Zirconia is a promising metal-free framework material that can be used to construct all-ceramic resin-bonded restorations in modern minimally invasive dentistry. The lack of a durable bond to zirconia is the major limitation against its widespread use. A technique to promote adhesion to the zirconia

  10. Analysis of zirconia and alumina products and raw materials by X-ray fluorescence spectrometry

    International Nuclear Information System (INIS)

    Boix, A.; Draignaud, M.; Debras-Guedon, J.

    1975-01-01

    An X-ray fluorescence spectrometric method of analysis for various raw materials and materials based on zirconia, alumina and silica was developed. The measurements were made on beads made from the sample and a borax based flux, in the proportions 1:10. A repeatability test allowed the relative standard deviation to be estimated for the three main constituents: SiO 2 , Al 2 O 3 , ZrO 2 : it is at the level of 1%. The element analyzed are: Si, Al, Fe, Ti, Ca, Hf and Zr [fr

  11. Synthesis, characterization and biological behavior of some Schiff's and Mannich base derivatives of Lamotrigine

    Directory of Open Access Journals (Sweden)

    A.A. Kulkarni

    2017-02-01

    Full Text Available A series of various Schiff's and Mannich base derivatives (N1–2 & ND1–6 of Lamotrigine with isatin and substituted isatin were synthesized to get more potent anticonvulsant agents. The starting material for the synthesis of various new Schiff's and Mannich base derivatives was isatin (1H-indole- 2, 3-dione which in turn was prepared from substituted isonitrosoacetanilide using aniline. Lamotrigine reacts with isatin & substituted isatin gave Schiff's bases (N1–2 which on reaction with various secondary amines (dimethylamine, diethylamine, morpholine produced Mannich bases (ND1–6. The structures of newly synthesized compounds were characterized by using TLC, UV, FT-IR, 1HNMR and studied for their anticonvulsant activity. Anticonvulsant activity of all the derivatives was evaluated by MES method using phenobarbitone sodium & Lamotrigine as standard drugs and % reduction of time spent by animals in extension, flexion, clonus, and stupor phase were noted. Compounds ND-4 and ND-6 showed significant anticonvulsant activity when compared with that of standard drugs. The remaining all compounds show moderate activity. Biological activity data of the synthesized derivatives revealed that, the synthesized derivatives are good anticonvulsant agents as compared to Lamotrigine.

  12. CAD/CAM Zirconia vs. slip-cast glass-infiltrated Alumina/Zirconia all-ceramic crowns: 2-year results of a randomized controlled clinical trial

    Directory of Open Access Journals (Sweden)

    Murat Cavit Çehreli

    2009-02-01

    Full Text Available The aim of this randomized controlled clinical trial was to compare the early clinical outcome of slip-cast glass-infiltrated Alumina/Zirconia and CAD/CAM Zirconia all-ceramic crowns. A total of 30 InCeram® Zirconia and Cercon® Zirconia crowns were fabricated and cemented with a glass ionomer cement in 20 patients. At baseline, 6-month, 1-year, and 2-year recall appointments, Californian Dental Association (CDA quality evaluation system was used to evaluate the prosthetic replacements, and plaque and gingival index scores were used to explore the periodontal outcome of the treatments. No clinical sign of marginal discoloration, persistent pain and secondary caries was detected in any of the restorations. All InCeram® Zirconia crowns survived during the 2-year period, although one nonvital tooth experienced root fracture coupled with the fracture of the veneering porcelain of the restoration. One Cercon® Zirconia restoration fractured and was replaced. According to the CDA criteria, marginal integrity was rated excellent for InCeram® Zirconia (73% and Cercon® Zirconia (80% restorations, respectively. Slight color mismatch rate was higher for InCeram® Zirconia restorations (66% than Cercon® Zirconia (26% restorations. Plaque and gingival index scores were mostly zero and almost constant over time. Time-dependent changes in plaque and gingival index scores within and between groups were statistically similar (p>0.05. This clinical study demonstrates that single-tooth InCeram® Zirconia and Cercon® Zirconia crowns have comparable early clinical outcome, both seem as acceptable treatment modalities, and most importantly, all-ceramic alumina crowns strengthened by 25% zirconia can sufficiently withstand functional load in the posterior zone.

  13. Zirconia coating for enhanced thermal stability of gold nanoparticles

    Science.gov (United States)

    Pastre, A.; Cristini-Robbe, O.; Bois, L.; Chassagneux, F.; Branzea, D.; Boé, A.; Kinowski, C.; Raulin, K.; Rolland, N.; Bernard, R.

    2016-01-01

    This paper describes a rapid, simple and one-step method for the preparation of 2-4 nm diameter zirconia-coated gold nanoparticles at room temperature. These nanoparticles were synthesized by two simultaneous processes: the chemical reduction of tetrachloroauric acid with sodium borohydride and the formation of zirconia sol-gel matrices. All the gold nanoparticle sols were characterized by UV-visible absorption and transmission electron microscopy to determine the nanoparticle size and shape. The synthesis method is a combination of a polymeric structure of the amorphous zirconia and the use of a strong reducing agent, and it yields to very small quasi-spherical gold nanoparticles at room temperature. The thermal stability up to 1200 °C of the coated nanoparticles was studied by x-ray diffraction. The metastable tetragonal phase of the zirconia coating was obtained at 400 °C, and a progressive transformation from tetragonal to monoclinic phases of the zirconia coating was observed up to 1100 °C. After the heat treatment at 400 °C, the crystallite size of the gold nanoparticles was about 29 nm, and it remained unchanged from 400 °C to 1200 °C. These results are promising for the development of such materials as doping elements for optical fiber applications.

  14. Gloss and Surface Roughness of Anterior Pediatric Zirconia Crowns.

    Science.gov (United States)

    Theriot, Adrien L; Frey, Gary N; Ontiveros, Joe C; Badger, Gary

    2017-09-15

    The purpose of this study was to determine gloss and surface roughness (Ra) of pediatric anterior zirconia crowns. Gloss of labial and lingual surfaces of pediatric anterior zirconia crowns from three manufacturers was measured on 20 specimens using a small area gloss meter on each. Ra (μm) was measured using a contact-type surface profilometer. Data were evaluated by analysis of variance and pair-wise comparison at the 0.05 level of significance. There were statistically significant interactions between surface location and crown type for both gloss and Ra scores. NuSmile had higher mean gloss scores and lower mean Ra scores than both Kinder Krowns and EZCrowns. Kinder Krowns showed lower mean gloss scores and higher Ra scores than other crown groups. Among all crowns, there was a trend of higher mean gloss paired with lower mean surface roughness, and lower mean gloss paired with higher mean Ra. Hand smoothed followed by mechanically polished zirconia crowns (NuSmile) displayed the highest mean gloss and lowest mean Ra compared to hybrid polishedglazed zirconia crowns (Kinder Krowns, EZCrowns). Of the hybrid polished-glazed zirconia crowns, Kinder Krowns displayed the lowest mean gloss and highest mean Ra.

  15. Regioselective synthesis of fraxinellone-based hydrazone derivatives as insecticidal agents.

    Science.gov (United States)

    Guo, Yong; Yan, Yuan-Yuan; Yang, Chun; Yu, Xiang; Zhi, Xiao-Yan; Xu, Hui

    2012-09-01

    In continuation of our program aimed at the discovery and development of natural products-based insecticidal agents, twenty-three new fraxinellone-based hydrazone derivatives were smoothly prepared from fraxinellone via regioselectively allylic oxidation in the presence of selenium dioxide or chromium trioxide under microwave irradiation and subsequent condensation with hydrazides or hydrazines. Their insecticidal activity was evaluated against the pre-third-instar larvae of Mythimna separata Walker in vivo. Especially compounds 6d and 7a displayed the most pronounced insecticidal activity compared with toosendanin, a commercial botanical insecticide derived from Melia azedarach. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. Processing of alumina and zirconia nano-powders and compacts

    Energy Technology Data Exchange (ETDEWEB)

    Wu Yujie; Bandyopadhyay, Amit; Bose, Susmita

    2004-08-25

    Magnesia-doped alumina and yttria-doped zirconia nano-powders were synthesized using sucrose as a chelating agent and template material from the aqueous solutions of aluminium nitrate, magnesium nitrate, ytrrium nitrate and zirconyl nitrate, respectively. Synthesis parameters were optimized with varying sucrose to metal ion ratio, calcinations time, and temperature to produce these nano-powders. As-synthesized powders were characterized by room temperature X-ray diffraction, BET surface area analyzer and transmission electron microscopy. Y{sub 2}O{sub 3}-ZrO{sub 2} nano-powders had particle size in the range of 80-200 nm with specific average surface area of 119 m{sup 2}/g and for MgO-Al{sub 2}O{sub 3} powders, particle sizes were 30-200 nm with the specific average surface area of 250 m{sup 2}/g. Our results indicate that this synthesis method is a versatile one and can be applied to a variety of oxide-based materials to form nano-powders. Nano-powders were compacted uniaxially and densified in a muffle furnace. Sintered discs were used for hardness testing and density measurements, as well as for microstructural characterization.

  17. Analytical derivation: An epistemic game for solving mathematically based physics problems

    Science.gov (United States)

    Bajracharya, Rabindra R.; Thompson, John R.

    2016-06-01

    Problem solving, which often involves multiple steps, is an integral part of physics learning and teaching. Using the perspective of the epistemic game, we documented a specific game that is commonly pursued by students while solving mathematically based physics problems: the analytical derivation game. This game involves deriving an equation through symbolic manipulations and routine mathematical operations, usually without any physical interpretation of the processes. This game often creates cognitive obstacles in students, preventing them from using alternative resources or better approaches during problem solving. We conducted hour-long, semi-structured, individual interviews with fourteen introductory physics students. Students were asked to solve four "pseudophysics" problems containing algebraic and graphical representations. The problems required the application of the fundamental theorem of calculus (FTC), which is one of the most frequently used mathematical concepts in physics problem solving. We show that the analytical derivation game is necessary, but not sufficient, to solve mathematically based physics problems, specifically those involving graphical representations.

  18. Design of Chitosan and Its Water Soluble Derivatives-Based Drug Carriers with Polyelectrolyte Complexes

    Directory of Open Access Journals (Sweden)

    Qing-Xi Wu

    2014-12-01

    Full Text Available Chitosan, the cationic polysaccharide derived from the natural polysaccharide chitin, has been studied as a biomaterial for more than two decades. As a polycationic polymer with favorable properties, it has been widely used to form polyelectrolyte complexes with polyanions for various applications in drug delivery fields. In recent years, a growing number of studies have been focused on the preparation of polyelectrolyte complexes based on chitosan and its water soluble derivatives. They have been considered well-suited as biomaterials for a number of vital drug carriers with targeted/controlled release profiles, e.g., films, capsules, microcapsules. In this work, an overview highlights not only the favorable properties of chitosan and its water soluble derivatives but also the good performance of the polyelectrolyte complexes produced based on chitosan. Their various types of applications as drug carriers are reviewed in detail.

  19. Design of Chitosan and Its Water Soluble Derivatives-Based Drug Carriers with Polyelectrolyte Complexes

    Science.gov (United States)

    Wu, Qing-Xi; Lin, Dong-Qiang; Yao, Shan-Jing

    2014-01-01

    Chitosan, the cationic polysaccharide derived from the natural polysaccharide chitin, has been studied as a biomaterial for more than two decades. As a polycationic polymer with favorable properties, it has been widely used to form polyelectrolyte complexes with polyanions for various applications in drug delivery fields. In recent years, a growing number of studies have been focused on the preparation of polyelectrolyte complexes based on chitosan and its water soluble derivatives. They have been considered well-suited as biomaterials for a number of vital drug carriers with targeted/controlled release profiles, e.g., films, capsules, microcapsules. In this work, an overview highlights not only the favorable properties of chitosan and its water soluble derivatives but also the good performance of the polyelectrolyte complexes produced based on chitosan. Their various types of applications as drug carriers are reviewed in detail. PMID:25532565

  20. The Metal-Zirconia Implant Fixed Hybrid Full-Arch Prosthesis: An Alternative Technique for Fabrication.

    Science.gov (United States)

    Stumpel, Lambert J; Haechler, Walter

    2018-03-01

    The metal-resin hybrid full-arch prosthesis has been a traditionally used type of restoration for full-arch implant fixed dentures. A newer development has centered around the use of monolithic zirconia or zirconia veneered with porcelain. Being a ceramic, zirconia has the potential for fracture. This article describes a technique that utilizes a metal substructure to support a chemically and mechanically resinbonded shell of zirconia. The workflow is discussed, ranging from in-office master cast fabrication to the CAD/ CAM production of the provisional and the definitive metal-zirconia prosthesis. The article also highlights the advantages and disadvantages of various materials used for hybrid prostheses.

  1. Structure Characterization calculation of Tetragonal Zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Feng, J; Wang, X Y; Ren, X R; Huang, Z C; Pan, W [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing, 100084 (China); Zhou, R, E-mail: fengj09@mails.tsinghua.edu.cn, E-mail: panw@mail.tsinghua.edu.cn [Key Laboratory of Advanced Materials of Precious-Nonferrous Metals, Education Ministry of China, Kunming University of Science and Technology, Kunming 650093 (China)

    2011-10-29

    Structure characterization and elastic properties of tetragonal phase of zirconia have been investigated by density functional theory (DFT). The XRD spectrums and vibration properties of Raman active modes of T-ZrO{sub 2} were calculated and the results were compared with references. The calculated results have showed researchers may distinguish cubic and tetragonal phases used XRD spectrums in the 2 range of 72.5{sup 0}-75.5{sup 0}, 122{sup 0}-129{sup 0} and 138{sup 0}-148{sup 0}. The calculated vibrated properties of Raman active modes as follows: the modes of Zr-O stretching are 262.6, 486.2, and 641.6 cm{sup -1} the modes of Zr-O bending and O-O coupling are 344.4 and 606.9 cm{sup -1} and the modes of Zr-O-Zr or O-Zr-O bending is 141.2 cm{sup -1}.

  2. Mechanical behavior of mullite-zirconia composites

    Directory of Open Access Journals (Sweden)

    Sahnoune F.

    2010-06-01

    Full Text Available In this work, mechanical properties of mullite–zirconia composites synthesised through reaction sintering of Algerian kaolin, α-Al2O3, and ZrO2 were characterized. Phases present and their transformations were characterized using x-ray diffraction. Hardness H and fracture toughness KIC were measured by Vickers indentation using a Zwick microhardness tester. The flexural strength was measured through three point bending test using an Instron Universal Testing Machine. It was found that the increase of ZrO2 content (from 0 to 32wt.% decreased the microhardness of the composites from 14 to 10.8 GPa. However, the increase of ZrO2 content (from 0 to 24wt.% increased the flexural strength of the composites from 142 to 390 MPa then decreased it with further increase of ZrO2 content. Also, the fracture toughness increased from 1.8 to 2.9 MPa.m1/2 with the increase of ZrO2 content from 0 to 32 wt.%; and the rate of the increase decreased at higher fractions of ZrO2 content. The average linear coefficient of thermal expansion (within the range 50 to 1450°C for samples containing 0 and 16 wt.% ZrO2 sintered at 1600°C for 2 hours was 4.7 x10-6 K-1 and 5.2 x 10-6 K-1 respectively.

  3. Fracture toughness measurements on zirconia toughened ceramics

    International Nuclear Information System (INIS)

    El Sayed Ali, M.; Toft Soerensen, O.

    1986-12-01

    Three techniques for fracture toughness measurements on zirconia toughened ceramics were evaluated: the notched beam (NB) technique, the indentation fracture (IF) technique and the indentation strength in bending (ISB) technique. Using these techniques comparative measurements were performed on samples prepared by pressing (uniaxial) and sintering of four commercially available powder types. These were: Toya Soda (Japan) powders with the designations TZ3Y (2.86 mole% Y 2 O 3 ), TZ3YA (2.77 mole% Y 2 O 3 , 0.1 wt% Al 2 O 3 ) and TZ3Y20A (2.88 mole% Y 2 O 3 , 20 wt.% Al 2 O 3 ) and a powder supplied by Viking Chemicals (Denmark) designated as YP5Z-2.5 (2.5 mole% Y 2 O 3 ). The measurements showed that similar K Ic values were obtained with the IF- and ISB-techniques, which therefore are recommended for K Ic measurements. Too high values were, however, obtained with the NB-technique which therefore cannot be recommended. Finally, the measurements showed that a high temperature annealing is recommended prior to testing for the IF-technique. (author)

  4. A critical appraisal of the systematic review process: systematic reviews of zirconia single crowns.

    Science.gov (United States)

    Lang, Lisa A; Teich, Sorin T

    2014-06-01

    Systematic reviews analyze the data of published research in an effort to assemble the scientific evidence to help clinicians apply evidence-based information in decision making. The quality of systematic reviews varies greatly. The purpose of this study was to critically appraise the current systematic review process by evaluating systematic reviews that pertain to zirconia-based single crowns. The following PICO (patients, intervention, comparison, outcome) question was formulated: "In adults, how does the long-term prognosis of zirconia-based single crowns compare with conventional single crowns on natural teeth?" An electronic search was performed in PubMed and the Cochran Library for articles published in English between 1950 and October 2012. Additional manual searches were completed. To be included in the analysis, the study must have been a systematic review, published in an English-speaking peer-reviewed journal, and evaluated zirconia crowns on teeth. Two examiners qualitatively evaluated the publications with an Assessment of Multiple Systematic Reviews checklist and the Oxford Systematic Review Appraisal form. Three systematic reviews were identified that met the search criteria. Two studies met 5 of the 11 Assessment of Multiple Systematic Reviews criteria, whereas the third met only 1 criterion. The same 2 studies met 3 of the 5 Oxford Systematic Review Appraisal criteria and the third met only 2 criteria. Because of the variation in methodologies, systematic reviews should be interpreted cautiously. The Assessment of Multiple Systematic Reviews Checklist and the Oxford Systematic Review Appraisal Sheet are practical tools for appraising and determining the quality of systematic reviews. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  5. Cytotoxicity and biocompatibility of Zirconia (Y-TZP posts with various dental cements

    Directory of Open Access Journals (Sweden)

    Hyeongsoon Shin

    2016-08-01

    Full Text Available Objectives Endodontically treated teeth with insufficient tooth structure are often restored with esthetic restorations. This study evaluated the cytotoxicity and biological effects of yttria partially stabilized zirconia (Y-TZP blocks in combination with several dental cements. Materials and Methods Pairs of zirconia cylinders with medium alone or cemented with three types of dental cement including RelyX U200 (3M ESPE, FujiCEM 2 (GC, and Panavia F 2.0 (Kuraray were incubated in medium for 14 days. The cytotoxicity of each supernatant was determined using 3-(4,5-dimethylthiazole-2-yl-2,5-diphenyltetrazolium bromide (MTT assays on L929 fibroblasts and MC3T3-E1 osteoblasts. The levels of interleukin-6 (IL-6 mRNA were evaluated by reverse transcription polymerase chain reaction (RT-PCR, and IL-6 protein was evaluated by enzyme-linked immunosorbent assays (ELISA. The data were analyzed using one-way ANOVA and Tukey post-hoc tests. A p < 0.05 was considered statistically significant. Results The MTT assays showed that MC3T3-E1 osteoblasts were more susceptible to dental cements than L929 fibroblasts. The resin based dental cements increased IL-6 expression in L929 cells, but reduced IL-6 expression in MC3T3-E1 cells. Conclusions Zirconia alone or blocks cemented with dental cement showed acceptable biocompatibilities. The results showed resin-modified glass-ionomer based cement less produced inflammatory cytokines than other self-adhesive resin-based cements. Furthermore, osteoblasts were more susceptible than fibroblasts to the biological effects of dental cement.

  6. C60-based ebselen derivative: synthesis by bingel cyclopropanation and enhanced antioxidative and neuroprotective activity

    International Nuclear Information System (INIS)

    Xufeng Liu; Wenchao Guan; Wengshan Ke

    2007-01-01

    C 60 -based ebselen derivative 3 was synthesized through Bingel cyclopropanation of C 60 with the ebselen malonate 2. Compound 3 was obtained in 42% yield (based on consumed C 60 ) in a three-step synthesis starting from 2-(chloroseleno)benzoyl chloride and 2-(2aminoethoxy)ethanol. Its structure was confirmed by 1H NMR, 13 C NMR, IR, UV and FAB-MS spectroscopy analyses. In order to verify the enhanced antioxidative and neuroprotective activity of 3, a C 60 derivative (4), an ebselen derivative (2), and their mixture (4 plus 2 in equimolar ratio) were employed to treat cortical neuronal cells, following the same procedure used with 3 and at the same final concentration (30 μmol L -1 ). Cell viabilities of the four treated groups were estimated by LDH (lactic dehydrogenase) leakage and MTT (3-(4, 5-dimethylthiazole-2yl)-2,5-diphenyl-tetrazolium bromide) assays. Results showed that the antioxidative and protective activities of C 60 -based ebselen derivative 3 against H 2 O 2 -mediated neuronal injury (MTT(OD) 0.364 ± 0.028; LDH release (UL -1 ) 4.66 ± 0.28) were significantly higher than those of C 6 )0 derivative 4 (MTT(OD) 0.324 ± 0.025; LDH release (UL -1 ) 5.39 ± 0.17), ebselen derivative 2 (MTT(OD) 0.294 ± 0.021; LDH release (UL -1 ) 5.71 ± 0.27), and the mixture of 4 and 2 (MTT(OD) 0.310 ± 0.018; LDH release (UL -1 ) 5.54 ±0.39). These findings demonstrated that the combination of two molecular units with similar biological activities (C 60 and ebselen) may be a desirable way of obtaining new and more biologically effective C 60 -based compounds. (author)

  7. Ultrasonic characterization of zirconia-toughened alumina ceramics

    International Nuclear Information System (INIS)

    Phani, K.K.; Mukherjee, S.; Basu, D.

    1996-01-01

    Ultrasonic pulse-echo technique was used for the characterization of sintered zirconia-toughened alumina (ZTA) ceramics. The variation of the ultrasonic velocity and elastic constants with the volume fraction of zirconia in the alumina matrix was studied. The ultrasonic velocity variation in these materials also was modeled using a mean-value approach. The zirconia grains in ZTA were modeled by oblate spheroids, whose aspect ratio was estimated from the two-dimensional microstructure of the material using stereological relations. The aspect ratio was then used as a parameter to estimate the ultrasonic velocity variation in the material using self-consistent spheroidal inclusion theory, and the model was validated by comparing the estimated data with the measured velocity values, which showed very good agreement

  8. [Clinical evaluation of zirconia crowns for single posterior teeth].

    Science.gov (United States)

    Chen, Yuanhua; Meng, Xiangfeng; Yu, Qing

    2014-06-01

    To observe and evaluate the clinical performance of zirconia crowns made by CEREC inLab computer aided design/computer aided manufacturing(CAD/CAM) for posterior teeth. A total of 242 patients were implanted with zirconia crowns fabricated by CEREC inLab CAD/CAM. The crowns were evaluated by Modified US Public Health Service criteria at baseline, 6, 12, 24, and 36 months. The chi-square test was used to analyze the survival rate. All but five crowns were evaluated by an independent evaluator at baseline, 6, 12, 24, and 36 months. The survival rate declined with time. The A score percentage was above 85% at 36 months. The single zirconia crowns fabricated by CEREC inLab CAD/CAM demonstrate satisfactory clinical performance during a short period.

  9. Thermodynamic properties of some metal oxide-zirconia systems

    Science.gov (United States)

    Jacobson, Nathan S.

    1989-01-01

    Metal oxide-zirconia systems are a potential class of materials for use as structural materials at temperatures above 1900 K. These materials must have no destructive phase changes and low vapor pressures. Both alkaline earth oxide (MgO, CaO, SrO, and BaO)-zirconia and some rare earth oxide (Y2O3, Sc2O3, La2O3, CeO2, Sm2O3, Gd2O3, Yb2O3, Dy2O3, Ho2O3, and Er2O3)-zirconia system are examined. For each system, the phase diagram is discussed and the vapor pressure for each vapor species is calculated via a free energy minimization procedure. The available thermodynamic literature on each system is also surveyed. Some of the systems look promising for high temperature structural materials.

  10. Synthesis and antitumor evaluation of arctigenin derivatives based on antiausterity strategy.

    Science.gov (United States)

    Kudou, Naoki; Taniguchi, Akira; Sugimoto, Kenji; Matsuya, Yuji; Kawasaki, Masashi; Toyooka, Naoki; Miyoshi, Chika; Awale, Suresh; Dibwe, Dya Fita; Esumi, Hiroyasu; Kadota, Shigetoshi; Tezuka, Yasuhiro

    2013-02-01

    A series of new (-)-arctigenin derivatives with variably modified O-alkyl groups were synthesized and their preferential cytotoxicity was evaluated against human pancreatic cancer cell line PANC-1 under nutrient-deprived conditions. The results showed that monoethoxy derivative 4i (PC(50), 0.49 μM), diethoxy derivative 4h (PC(50), 0.66 μM), and triethoxy derivative 4m (PC(50), 0.78 μM) showed the preferential cytotoxicities under nutrient-deprived conditions, which were identical to or more potent than (-)-arctigenin (1) (PC(50), 0.80 μM). Among them, we selected the triethoxy derivative 4m and examined its in vivo antitumor activity using a mouse xenograft model. Triethoxy derivative 4m exhibited also in vivo antitumor activity with the potency identical to or slightly more than (-)-arctigenin (1). These results would suggest that a modification of (-)-arctigenin structure could lead to a new drug based on the antiausterity strategy. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  11. Influence of the Conditioning Method for Pre-Sintered Zirconia on the Shear Bond Strength of Bilayered Porcelain/Zirconia

    Directory of Open Access Journals (Sweden)

    Sebastian Spintzyk

    2016-09-01

    Full Text Available This study evaluated the bond strength of veneering porcelain with an experimental conditioner-coated zirconia. Pre-sintered Y-TZP specimens (n = 44 were divided in two groups based on conditioning type. After sintering, all sample surfaces were sandblasted and layered with veneering porcelain. Additionally, half of the specimens in each group underwent thermal cycling (10,000 cycles, 5–55 °C, and all shear bond strengths were measured. After testing, the failure mode of each fractured specimen was determined. Differences were tested by parametric and Fisher’s exact tests (α = 0.05. The differences in bond strength were not statistically significant. Adhesive fractures were dominantly observed for the non-thermal cycled specimens. After thermal cycling, the conditioner-coated group showed cohesive and mixed fractures (p = 0.0021, whereas the uncoated group showed more adhesive fractures (p = 0.0021. Conditioning of the pre-sintered Y-TZP did not change the shear bond strength of the veneering porcelain, but did improve the failure mode after thermal cycling.

  12. Influence of the Conditioning Method for Pre-Sintered Zirconia on the Shear Bond Strength of Bilayered Porcelain/Zirconia

    Science.gov (United States)

    Spintzyk, Sebastian; Yamaguchi, Kikue; Sawada, Tomofumi; Schille, Christine; Schweizer, Ernst; Ozeki, Masahiko; Geis-Gerstorfer, Jürgen

    2016-01-01

    This study evaluated the bond strength of veneering porcelain with an experimental conditioner-coated zirconia. Pre-sintered Y-TZP specimens (n = 44) were divided in two groups based on conditioning type. After sintering, all sample surfaces were sandblasted and layered with veneering porcelain. Additionally, half of the specimens in each group underwent thermal cycling (10,000 cycles, 5–55 °C), and all shear bond strengths were measured. After testing, the failure mode of each fractured specimen was determined. Differences were tested by parametric and Fisher’s exact tests (α = 0.05). The differences in bond strength were not statistically significant. Adhesive fractures were dominantly observed for the non-thermal cycled specimens. After thermal cycling, the conditioner-coated group showed cohesive and mixed fractures (p = 0.0021), whereas the uncoated group showed more adhesive fractures (p = 0.0021). Conditioning of the pre-sintered Y-TZP did not change the shear bond strength of the veneering porcelain, but did improve the failure mode after thermal cycling. PMID:28773885

  13. CONFAC Decomposition Approach to Blind Identification of Underdetermined Mixtures Based on Generating Function Derivatives

    NARCIS (Netherlands)

    de Almeida, Andre L. F.; Luciani, Xavier; Stegeman, Alwin; Comon, Pierre

    2012-01-01

    This work proposes a new tensor-based approach to solve the problem of blind identification of underdetermined mixtures of complex-valued sources exploiting the cumulant generating function (CGF) of the observations. We show that a collection of second-order derivatives of the CGF of the

  14. Single-Phase Phase-Locked Loop Based on Derivative Elements

    DEFF Research Database (Denmark)

    Guan, Qingxin; Zhang, Yu; Kang, Yong

    2017-01-01

    High-performance phase-locked loops (PLLs) are critical for power control in grid-connected systems. This paper presents a new method of designing a PLL for single-phase systems based on derivative elements (DEs). The quadrature signal generator (QSG) is constructed by two DEs with the same...

  15. Sensing of polymeric sensor-based rhodamine B derivative for metal ...

    Indian Academy of Sciences (India)

    ity after complexes with metal ions by activating a carbonyl group in a spirolactone or a spirolactam moiety [27–30]. The mechanism is based on the switch off/on of the spirocyclic moiety mediated by guests. In general, spirolactam formation of rhodamine derivatives is non-fluorescent, whereas its ring-opened amide system ...

  16. Effect of thermal aging on the erosion resistance of air plasma sprayed zirconia thermal barrier coating

    International Nuclear Information System (INIS)

    Janos, B.Z.; Lugscheider, E.; Remer, P.

    1999-01-01

    To increase the performance, efficiency and reliability of thermal barrier coatings, it is important to understand the influence of the microstructure on the erosion resistance. Therefore, the erosion behavior of air-plasma-sprayed 7 wt% yttria stabilized zirconia (7YSZ) thermal barrier coatings (TBC) at elevated temperatures was investigated. The paper focuses on both the porosity of the coating as well as the thermal pre-treatment of the ceramic. To simulate operating conditions on the ceramic samples, high-temperature erosion experiments at 1093 C were carried out on as-sprayed samples as well as on samples, thermally aged at different temperatures up to 1482 C in air prior to erosion testing. A significant dependence of erosion rate on porosity and thermal pre-treatment was found. Finally, a technique was developed to predict the erosion rates of air-plasma-sprayed 7YSZ TBCs independent of aging conditions or porosity levels. Erosion rates seem to be highly correlated to the micro-hardness of the zirconia TBC. A power-law model was empirically derived to estimate erosion rates of plasma-sprayed 7YSZ ceramic thermal barrier coatings. (orig.)

  17. Fabrication and Microstructure of Hydroxyapatite Coatings on Zirconia by Room Temperature Spray Process.

    Science.gov (United States)

    Seo, Dong Seok; Chae, Hak Cheol; Lee, Jong Kook

    2015-08-01

    Hydroxyapatite coatings were fabricated on zirconia substrates by a room temperature spray process and were investigated with regards to their microstructure, composition and dissolution in water. An initial hydroxyapatite powder was prepared by heat treatment of bovine-bone derived powder at 1100 °C for 2 h, while dense zirconia substrates were fabricated by pressing 3Y-TZP powder and sintering it at 1350 °C for 2 h. Room temperature spray coating was performed using a slit nozzle in a low pressure-chamber with a controlled coating time. The phase composition of the resultant hydroxyapatite coatings was similar to that of the starting powder, however, the grain size of the hydroxyapatite particles was reduced to about 100 nm due to their formation by particle impaction and fracture. All areas of the coating had a similar morphology, consisting of reticulated structure with a high surface roughness. The hydroxyapatite coating layer exhibited biostability in a stimulated body fluid, with no severe dissolution being observed during in vitro experimentation.